Battery pack and method for making same

ABSTRACT

A battery pack includes: a battery having a main surface; and a resin layer capable of being integrated with an armor member armoring the battery so that at least a part of the main surface of the battery is exposed and covering the main surface of the battery, wherein the resin layer is formed by curing a reaction curable resin having a viscosity of not less than 80 mPa·second to less than 1000 mPa·second and a thickness of the resin layer on the main surface of the battery ranges from 0.05 mm to smaller than 0.4 mm.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/080,192 filed Apr. 5, 2011, which application claimspriority to Japanese Priority Patent Application JP 2010-088540 filed inthe Japan Patent Office on Apr. 7, 2010, the entire content of which ishereby incorporated by reference.

BACKGROUND

1. Field of the Invention

This invention relates to a battery pack including a non-aqueouselectrolytic secondary battery and a method for making the same. Moreparticularly, the invention relates to a battery pack wherein anon-aqueous electrolytic secondary battery, a circuit board, and otherbattery pack components are integrated by resin molding and a methodmaking such a battery pack.

2. Description of the Related Art

In recent years, a number of portable electronic devices includingcamera-integrated video tape recorders, cell phones and portablepersonal computers have appeared on the market and their reduction insize and weight has been promoted. As such electronic devices arereduced in size and weight, it is required that battery packs used as aportable power supply therefor have a high energy, be downsized and belight in weight. A high-capacity lithium ion secondary battery is nowused as a battery for these battery packs.

The lithium ion secondary battery is provided with a battery elementhaving a positive electrode and a negative electrode capable of dopingand de-doping lithium ions, and the battery element is sealed in a metalcan or metal laminate film and is controlled by means of a circuit boardelectrically connected to the battery element. With existing lithium ionsecondary batteries, some battery pack is so configured that it isaccommodated into two vertically-divided accommodation cases along witha circuit board (see, for example, Japanese Patent Nos. 3556875,3614767, and 3643792).

With the battery pack configured to accommodate a lithium ion secondarybattery and a circuit board in the two vertically-divided accommodationcases, the accommodation cases need to have a satisfactory thickness soas to protect the lithium ion secondary battery and the circuit boardfrom external impact. In case where the two vertically-dividedaccommodation cases are bonded together by means of a double-facedadhesive tape or by ultrasonic welding, the accommodation cases shouldhave a thickness sufficient therefor. This in turn results in anincreased thickness and weight of the battery pack as a whole.

With the battery pack set forth in Japanese Patent No. 3614767, there isused a metal can-armored lithium ion secondary battery and thus, a highdimensional accuracy is likely to be obtained. However, the thicknessand weight of the battery pack increase. In contrast thereto, withbattery packs making use of a laminated lithium ion secondary batteryarmored with a laminate film, they can be made thinner and lighter inweight than the battery packs using the lithium ion battery armored witha metal can.

On the other hand, with the battery pack using a laminated lithium ionsecondary battery, the dimensional variation of a battery element is sogreat that a difficulty is involved in enhancing a dimensional accuracyand mechanical strength is inconveniently low.

SUMMARY

For a battery pack making use of a laminated lithium ion secondarybattery, there has been proposed an armor case-free battery pack. Inthis battery pack, a circuit board, etc., are assembled with thelaminated lithium ion secondary battery, which is temporarily mounted ina molding space of a mold for forming a resin molding. A molten resin isinjected into the molding space and subsequently cured to obtain thebattery pack. In the battery pack, the resin molding forms part of anarmor case of the battery pack and also serves to integrally fix acircuit board, connection terminals and a battery therewith.

In this battery pack, the laminated lithium ion secondary battery isused, with the attendant drawback that mechanical strength is low. Wehave found that this drawback can be overcome in such a way that whenthe thickness of the resin molding at a portion covering the sidesurfaces of the lithium ion secondary battery is greater than thethickness of the resin molding at portions covering the main surfaces ofthe battery, mechanical strength is improved.

However, in the case where the portion of the resin molding covering theside surfaces of the battery is greater in thickness than the resinmolded portion covering the main surfaces of the battery, mechanicalstrength is, in fact, improved. Nevertheless, upon the resin molding, aresin melt preferentially flows into a molding space that has been sodesigned as to secure a given thickness of the resin molding at aportion covering the side surfaces of the lithium ion secondary battery,for which a coverage failure takes place wherein part of the mainsurfaces is not covered with the molded resin, with the attendantproblem that the characteristics of the battery pack lower. In casewhere the resin molded portion covering the main surface of thesecondary battery is formed as thin, it is required to suppress theoccurrence of the coverage failure of the secondary battery.

Accordingly, it is desirable to provide a battery pack that is able tosuppress coverage failure thereby suppressing the battery packcharacteristics from lowering and also to provide a method for makingsuch a battery pack.

According to one embodiment of the invention, there is provided abattery pack including: a battery having a main surface; and a resinlayer capable of being integrated with an armor member armoring thebattery so that at least a part of the main surface of the battery isexposed and covering the main surface of the battery, wherein the resinlayer is formed by curing a reaction curable resin having a viscosity ofnot less than 80 mPa·second to less than 1000 mPa·second and a thicknessof the resin layer on the main surface of the battery ranges from 0.05mm to smaller than 0.4 mm.

According to another embodiment of the invention, there is provided amethod for making a battery pack including the steps of assembling abattery having main surfaces and an armor member armoring the battery insuch a way as to permit at least a part of the main surfaces of thebattery to be exposed, placing the assembled battery and the armormember in a molding space in a mold, charging a reaction curable resinhaving a viscosity of from 80 mPa·second to less than 1000 mPa·secondinto the mold, and curing the reaction curable resin so that a resinlayer covering the main surfaces of the battery is formed a thickness offrom 0.05 mm to smaller than 0.4 m.

In these embodiments, the resin layer covering the main surfaces of thebattery is obtained by curing the reaction curable resin having aviscosity of from 80 mPa·second to less than 1000 mPa·second. In doingso, the resin layer having a thickness of from 0.05 mm to smaller than0.4 mm is formed on the main surfaces of the battery, thereby enablingthe coverage failure of the battery pack to be avoided.

According to the invention, coverage failure can be avoided and thus,battery pack characteristics can be suppressed from lowering.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are, respectively, a schematic view showing aconfiguration example of a battery pack according to an embodiment ofthe invention;

FIGS. 2A and 2B are, respectively, a schematic sectional view showing aconfiguration example of the battery pack according to the embodiment ofthe invention;

FIG. 3 is an exploded, perspective view of a configuration example ofthe battery;

FIG. 4 is a perspective view showing a configuration example of abattery element:

FIGS. 5A to 5D are, respectively, a schematic view illustrating thesteps of making the battery pack;

FIGS. 6A and 6B are, respectively, a schematic view showing aconfiguration example of a battery pack according to another embodimentof the invention;

FIGS. 7A and 7B are, respectively, a schematic view showing aconfiguration example of a battery pack according to a furtherembodiment of the invention;

FIGS. 8A and 8B are, respectively, a sectional view showing aconfiguration example of the battery pack according to the furtherembodiment of the invention;

FIGS. 9A and 9B are, respectively, a schematic view showing aconfiguration example of a battery pack according to a still furtherembodiment of the invention;

FIGS. 10A and 10B are, respectively, a sectional view showing aconfiguration example of the battery pack according to the still furtherembodiment of the invention;

FIGS. 11A and 11B are, respectively, a schematic view showing aconfiguration example of a battery pack according to still anotherembodiment of the invention;

FIGS. 12A and 12B are, respectively, a sectional view showing aconfiguration example of the battery pack according to the still anotherembodiment of the invention;

FIGS. 13A and 13B are, respectively, a schematic view showing aconfiguration example of a battery pack according to yet anotherembodiment of the invention;

FIG. 14 is a sectional view showing a configuration example of thebattery pack according to the yet another embodiment of the invention;

FIGS. 15A and 15B are, respectively, a schematic view illustrating aflow channel control function of a spacer;

FIGS. 16A and 16B are, respectively, a schematic view showing an exampleof a configuration of the spacer;

FIGS. 17A and 17B are, respectively, a schematic view showing aconfiguration example of a battery pack according to another embodimentof the invention;

FIG. 18 is a sectional view showing a configuration example of thebattery pack according to the another embodiment of the invention; and

FIGS. 19A and 19B are, respectively, a schematic view illustrating themeasurement of thickness.

DETAILED DESCRIPTION

Embodiments of the present application will be described below in detailwith reference to the drawings.

The embodiments of the invention are described with reference to theaccompanying drawings wherein like reference numerals indicate likeparts or members throughout the drawings, which are not repeatedlyillustrated herein.

The embodiments are described in the following order.

1. First embodiment (first example of a battery pack) 2. Secondembodiment (second example of a battery pack) 3. Third embodiment (thirdexample of a battery pack) 4. Fourth embodiment (fourth example of abattery pack) 5. Fifth embodiment (fifth example of a battery pack) 6.Sixth embodiment (sixth example of a battery pack) 7. Seventh embodiment(seventh example of a battery pack) 8. Other embodiment (a variation)

1. First Embodiment

(Structure of a Battery Pack)

A battery pack according to a first embodiment of the invention is nowdescribed. FIG. 1A is an exploded, perspective view showing aconfiguration example of a battery pack according to a first embodimentof the invention. FIG. 1B is an appearance perspective view showing aconfiguration example of the battery pack according to the firstembodiment of the invention. FIG. 2A is a sectional view taken along theline a-a′ of FIG. 1B. FIG. 2B is a sectional view taken along the lineb-b′ of FIG. 1B.

As shown in FIGS. 1A and 1B, this battery pack includes a frame 30, abattery 10 and a circuit board 33, which are essential componentelements of the battery pack. The battery pack is provided with otherparts, which are connected to the essential component elements and/orarranged in position of the essential component elements and include aPTC (Positive Temperature Coefficient) protecting tape 31, a PTC element32, a negative electrode fitting 35 and a submergence detecting seal 36capable of color change when deposited with moisture. This battery packis a substantially rectangular parallelepiped-shaped resin molded bodywherein the battery 10, circuit board 33 and other parts such as the PTCelement 32 and the frame 30 are assembled to obtain an assembly and thisassembly is integrated by resin molding of a reaction curable resin. Inthis battery pack, the assembly of the battery 10, circuit board 33 andother parts including the PTC element 32 are armored with the frame 30and an armor member 40 made of the reaction curable resin.

As shown in FIGS. 2A and 2B, the battery is covered entirely with thearmor member 40. Moreover, the battery 10 is covered through the armormember 40 with the frame 30 at the side surfaces and at part of theupper and lower surfaces thereof. In the battery pack, a thickness D1(which may be hereinafter referred to arbitrarily as maximum surfacethickness D1) of the armor member on the upper and lower surfaces, whichare the main surfaces of the battery, is preferably from 0.05 mm tosmaller than 0.4 mm per unit surface, more preferably not larger than0.25 mm, in order to more improve a volume energy density. In addition,a thickness D2 of the armor member covering a side surface of thebattery 10 (hereinafter referred to arbitrarily as short side thicknessD2) and a thickness D3 (hereinafter referred to arbitrarily as long sidethickness D3) are preferably from 1.2 times to 6 times the maximumsurface thickness D1, respectively, so as to improve strength. In orderto more improve the strength, they are more preferably at 2 times to notgreater than 4 times the maximum surface thickness D1.

It will be noted that the maximum surface thickness D1 means an averagethickness in case where the thickness of the armor member 40 startingfrom the main surface of the battery 10 as an initial point ofmeasurement is measured at three points in the vicinity of the center.The short side thickness is determined while setting the most projectedpoint along the short side as a starting point of measurement and thesurface of the battery pack as an end point of the measurement. That is,it means a length of the armored portion along the short side. The longside thickness D3 is determined while setting the most projected pointalong the length of the battery 10 as a starting point of measurementand the surface of the battery pack as an end point of the measurement.That is, this thickness corresponds to a length of the armored portionalong the length.

(Battery)

An instance of the battery 10 is now illustrated. As shown in FIGS. 3and 4, the battery 10 is one wherein a battery element 20 having apositive electrode 21 and a negative electrode 22 convolutely wound orlaminated through separators 23 a, 23 b is packed with a laminated film27 serving as a packaging material. As is particularly shown in FIG. 3,the battery element 20 is accommodated in a rectangle-shaped recess 27 aformed in the packaging laminate film 27 and the peripheral portions(three sides except for the bent portion) are heat sealed. Portionsbonded with the laminate film 27 are terrace portions. The terraceportions at opposite sides of the recess 27 a are folded toward thedirection of the recess 27 a.

It will be noted that the laminate film 27 serving as a packagingmaterial may be a metal laminated film, e.g. an aluminum laminate film.The aluminum laminate film is preferably one that is adapted for drawingand is suited for forming the recess 27 a accommodating the batteryelement 20 therein.

The aluminum laminate film has a laminate structure wherein an aluminumlayer is provided on opposite sides thereof with an adhesive layer and asurface protecting layer. The aluminum laminate film preferably has, inthe order as viewed from the inner side i.e. the surface side of thebattery element 20, a cast polypropylene layer (CPP layer) serving as anadhesive layer, an aluminum layer used as a metal layer, and a nylonlayer or polyethylene terephthalate layer (PET layer) serving as asurface protective layer.

As shown in FIG. 4, a band-shaped positive electrode 21, a separator 23a, a band-shaped negative electrode 22 disposed in face-to-face relationwith the positive electrode 21, and a separator 23 b are successivelylaminated and the resulting laminate is convolutely wound along thelength thereof. The positive electrode 21 and negative electrode 22 are,respectively, coated with a gel electrolyte 24 on opposite sidesthereof. A positive electrode lead 25 a connected to the positiveelectrode 21 and a negative electrode lead 25 b connected to thenegative electrode 22 extend from the battery element 20, respectively.The positive electrode lead 25 a and the negative electrode lead 25 bare, respectively, covered with resin piece sealants 26 a and 26 b, suchas of a maleic anhydride-modified polypropylene (PP).

The components of the battery 10 are more particularly described below.It should be noted herein that the invention is applicable to thosebatteries or cells other than the battery set out hereinbelow. As toelectrolytes, for example, there may be used not only gel electrolytes,but also liquid or solid electrolytes.

[Positive Electrode]

The positive electrode 21 is one wherein a positive-electrode activematerial layer containing a positive electrode active material is formedon opposite sides of a positive electrode current collector. As thecurrent collector, there may be used a metallic foil such as, forexample, an aluminum (Al) foil a nickel (Ni) foil or a stainless steel(SUS) foil.

The positive-electrode active material layer is formed, for example, ofa positive-electrode active material, a conducting agent, and a binder.The positive-electrode active material used is a composite oxide oflithium and a transition metal mainly composed of Li_(x)MO₂ wherein Mrepresents at least one transition metal, and x may differ depending onthe charge or discharge conditions of battery and is generally a valuewithin a range of not smaller than 0.05 to not larger than 1.10. Thetransition metal of the lithium composite oxide may be cobalt (Co),nickel (Ni) or manganese (Mg).

Specific examples of the lithium composite oxide include lithiumcobaltate (LiCoO₂), lithium nickelate (LiNiO₂), lithium manganate(LiMg₂O₄) and the like. Alternatively, there may be also used solidsolutions wherein part of a transition metal is replaced by otherelement. For example, mention is made of lithium nickel cobalt compositeoxides (e.g. LiNi_(0.5)Ci_(0.5)O₂, LiNi_(0.8)Ci_(0.2)O₂ and the like).These lithium composite oxides are able to generate high voltage and areexcellent in energy density. Still alternatively, there may be usedphosphate compounds having an olivine structure, such as lithium ironphosphate (LiFePO₄), Li_(x)Fe_(1-y)M2_(y)PO₄ wherein M2 represents atleast one of the group consisting of manganese (Mn), nickel (Ni), cobalt(Co), zinc (Zn) and magnesium (Mg) and x is a value within a range of0.9≦x≦1. Yet alternatively, there may be used as a positive electrodeactive material lithium-free metal sulfides or metal oxides such asTiS₂, MoS₂, NbSe₂, V₂O₅ and the like. These may be used in admixture ofa plurality of these materials as a positive electrode active material.

The conductive materials include, for example, carbon materials such ascarbon black, graphite and the like. The binders used include, forexample, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE)and the like. The solvents include, for example, N-methyl-2-pyrrolidone(NMP) and the like.

[Negative Electrode]

The negative electrode 22 is one obtained by forming a negativeelectrode active layer containing a negative electrode active materialon opposite sides of a current collector for negative electrode. Thecurrent collector includes a metallic foil such as, for example, acopper (Cu) foil, a nickel (Ni) foil, a stainless steel (SUS) foil orthe like.

The negative electrode active material layer is formed, for example, ofa negative electrode active material and, if necessary, a conductivematerial and a binder. The negative electrode active material usedincludes a lithium metal, a lithium alloy or a carbon material capableof doping and de-doping lithium, or a composite material of a metallicmaterial and a carbon material. In particular, as a carbon materialcapable of doping or de-doping lithium, mention is made of graphite,hardly graphitizable carbon, readily graphitizable carbon and the like.More specifically, there may be used carbon materials such as pyrolyzedcarbons, cokes (e.g. pitch coke, needle coke, and petroleum coke),graphites, glassy carbons, fired organic polymers (those obtained byfiring and graphitizing phenolic resins, furan resins and the like atappropriate temperatures), carbon fibers, active carbon and the like.Moreover, those materials capable of doping and de-doping lithiuminclude polymers such as polyacetylene, polypyrrole and the like andoxides such as SnO₂ and the like.

Although various types of metals are usable as a material alloyable withlithium, there are frequently used tin (Sn), cobalt (Co), indium (In),aluminum (Al), silicon (Si) and alloys thereof. Where metallic lithiumis used, it is not always necessary that powder be coated as a film byuse of a binder, but a rolled lithium sheet may be used.

The binders used include polyvinylidene fluoride (PVdF), styrenebutadiene rubber (SBR), etc. The solvents include, for example,N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK) and the like.

[Electrolyte]

For an electrolyte, electrolytic salts and non-aqueous solvents, bothordinarily used in lithium ion secondary batteries, are usable. Thenon-aqueous solvents include ethylene carbonate (EC), propylenecarbonate (PC), γ-butyrolactone, dimethyl carbonate (DMC), diethylcarbonate (DEC), ethylmethyl carbonate (EMC), dipropyl carbonate (DPC),ethylpropyl carbonate (EPC) and the above compounds wherein the hydrogenof the carbonate ester is replaced by a halogen. These solvents may beused singly or in admixture as having a given formulation of a pluralitythereof.

The electrolytic salts are ones capable of being dissolved innon-aqueous solvents, wherein cations and anions are in combination. Thecation includes an alkali metal or an alkaline earth metal. The anionincludes Cl⁻, Br⁻, I⁻, SCN⁻, ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻, CF₃SO₃ ⁻ or the like.More specifically, mention is made of lithium trifluorophosphate(LiPF₆), lithium tetrafluoroborate (LiBF₄), lithiumbis(trifluoromethanesulfonyl)imide (LiN(CF₃SO₂)₂), lithiumbis(pentafluoromethanesulfonyl)imide (LiN(C₂F₅SO₂)₂) lithium perchlorate(LiClO₄) and the like. As to the concentration of the electrolyte, noproblem is involved if the electrolyte is able to be dissolved insolvent and the lithium ion concentration is preferably within a rangeof from 0.4 mol/kg to 2.0 mol/kg relative to a non-aqueous solvent.

If a polymeric electrolyte is used, there can be obtained such a polymerelectrolyte by mixing a non-aqueous solvent and an electrolytic salt toprovide a gel electrolyte, and taking the gel electrolyte in a matrixpolymer. The matrix polymer has a characteristic of compatibility with anon-aqueous solvent. As such a matrix polymer, there are used a siliconegel, an acrylic gel, an acrylonitrile gel, a polyphosphazene-modifiedpolymer, polyethylene oxide, polypropylene oxide, and compositepolymers, crosslinked polymers and modified polymers thereof. Thefluorine-based polymers include polyvinylidene fluoride (PVdF),copolymers containing repeating units of vinylidene fluoride (VdF) andhexafluoropropylene (HFP), copolymers containing repeating units ofvinylidene fluoride (VdF) and trifluoroethylene (TFE) and the like.These polymers may be used singly or in combination of two or more.

[Separator]

The separators 23 a and 23 b are, respectively, constituted, forexample, of porous membranes made of polyolefin-based materials such aspolypropylene (PP) or polyethylene or inorganic materials such asceramic non-woven fabrics. The laminate structures of these two or moreporous membranes may be used. Among them, porous films of polyethyleneor polypropylene are most effective.

In general, the thickness of the separator is preferably in the range offrom 5 μm to 50 μm, more preferably from 7 μm to 30 μm. If the separatoris too thick, a fill of an active material lowers, resulting in areduced battery capacity and also reduced ion conductivity, therebylowering current characteristics. In contrast, too thin a separatorlowers the mechanical strength of film.

(Circuit Board)

The circuit board 33 is mounted with a charge/discharge FET (fieldeffect transistor), a protecting circuit including IC and carrying outmonitoring of a secondary battery and the control of thecharge/discharge FET, an ID resistor for discriminating a battery pack,a connector connected to outside and the like. The circuit board 33 isprovided, for example, with three contact points.

The charge/discharge control FET and the protecting circuit including ICand carrying out the control of the charge/discharge control FET monitora voltage of the secondary battery wherein if the voltage exceeds 4.3 Vto 4.4 V, the charge/discharge control FET is turned off to prohibitcharge. Moreover, if a terminal voltage of the secondary battery isoverdischarged to a level of discharge prohibition voltage so that thesecondary battery voltage becomes lower than a discharge prohibitionvoltage, the discharge control FET is turned off thereby prohibitingdischarge.

(PTC Element)

The PTC element 32 is a part, which serves to interrupt a currentcircuit when the battery becomes high in temperature thereby preventingthe thermal runaway of the battery. The PTC element 32 is, for example,in series connection with the battery 10 and when the temperature of thebattery 10 is higher than a preset temperature, the electric resistancethereof abruptly increases, so that the current passing to the battery10 is substantially interrupted.

(Frame)

The frame 30 is a resin molded product, which covers through an armormember 40 part of an upper surface (i.e. a face at a side where therecess 27 a is formed) and a lower surface of the battery 10, a frontsurface (i.e. a face at a side where leads are extending), a rearsurface, and a left side surface and a right side surface.

The frame 30 is preferably made of a thermoplastic resin such as apolycarbonate, polypropylene, a polyamide or the like. This is becausethe use of a thermoplastic resin that is shorter in molding cycle than athermosetting resin is responsible for a quick and inexpensive supportagainst geometric variations such as of top and bottom sides suffering agreat switching frequency as a battery pack.

The frame 30 corresponds to the shape of the battery 10 with respect tothe front surface, rear surface, left side surface, right side surface,upper surface and lower surface and forms a space wherein the battery 10can be encased. The upper and lower surfaces of the frame 30 are,respectively, so shaped as to be partly cut away inside the surface in arectangular form so as to allow part of the upper and lower surfaces ofthe battery 10 to be exposed when assembled with the battery.

The frame 30 has a space capable of accommodating the circuit board 33at the inner side of the front surface and the circuit board 33 isplaced in this space. The circuit board 33 is in intimate contact withand secured to the inner side surface of the frame 30 such as, forexample, by means of rivets. The riveted, intimate contact and fixing ofthe circuit board with the inner surface of the frame 30 can prevent areaction curable resin having high fluidity from flowing toward theterminal faces of the circuit board 33. As will be describedhereinafter, in the course of the molding step of the reaction curableresin, reliable positioning of the circuit board 33 is possible. At thefront of the frame 30, a plurality of openings 34 are provided and thecircuit board 33 accommodated in the frame 30 ensures an approach tooutside through the openings 34 at contact points thereof. It will benoted that a resin molded board, made of a resin such as a polyamide,along with the frame 30 may be used as the circuit board 33.

(Armor Member)

The armor member 40 is formed of a reaction curable resin such as athermosetting resin curable by thermal reaction, a UV-curable resincurable by reaction under UV light or the like. The armor member 40 is aresin molded member formed by curing of a reaction curable resin.

(Reaction Curable Resin)

The reaction curable resin includes at least one member selected fromurethane resins, epoxy resins, acrylic resins, silicone resins, anddicyclopentadiene resin. Of these, at least one selected from urethaneresins, epoxy resins, acrylic resins and silicone resins is preferred.

(Urethane Resin)

The urethane resins are prepared from polyols and polyisocyanates.Preferred urethane resins include insulating polyurethane resins definedbelow. The insulating polyurethane resin means one that is able toprovide a cured product having a volume intrinsic resistance value(Ω·cm) of not lower than 10¹⁰ Ω·cm when determined under conditions of25+5° C. and 65+5% R.H. A preferred insulating polyurethane resin is onehaving a dielectric constant of not larger than 6 (1 MHz) and abreakdown voltage of not less than 15 KV/mm.

By controlling an oxygen content of a polyol, the concentration ofelution ions and the number in type of the elution ions, an insulatingcured product of insulating polyurethane resin is obtained as having avolume intrinsic resistance value of not less than 10¹⁰ Ω·cm, preferablynot less than 10¹¹ Ω·cm. Especially, when the volume intrinsicresistance value is at not less than 10¹¹ Ω·cm, the insulatingproperties of a cured product are kept good, ensuring integral sealingwith the protective circuit board of the secondary battery. The volumeintrinsic resistance value is measured according to the method describedin JIS C 2105. More particularly, the value is determined by applying ameasuring voltage of 500 V to a sample (thickness: 3 mm) and measuring60 seconds after the application under conditions of 25+5° C. and 65+5%R.H.

The urethane resins include polyester-based ones making use of polyesterpolyols, polyether-based ones making use of polyether polyols, and onesusing other types of polyols. These may be used singly or in admixtureof two or more. The polyol may contain powders. Such powders includeinorganic powders such as of calcium carbonate, aluminum hydroxide,aluminum oxide, silicon oxide, titanium oxide, silicon carbide, siliconnitride, calcium silicate, magnesium silicate, carbon and the like, andpowders of organic polymers such as polymethyl acrylate, polyethylacrylate, polymethyl methacrylate, polyethyl methacrylate, polyvinylalcohol, carboxymethyl cellulose, polyurethane, polyphenol and the like.These may be used singly or in admixture. The powders may besurface-treated, and polyurethane and polyphenol may be provided infoamed powder. In addition, the powders used in the embodiment of theinvention may include porous ones.

(Polyol)

(Polyester-Based One)

Polyester-based polyols are reaction products of fatty acids andpolyols. The fatty acids include, for example, hydroxy-containinglong-chain fatty acids such as recinoleic acid, oxycaproic acid,oxycapric acid, oxyundecanoic acid, oxylinoleic acid, oxystearic acidand oxyhexaundecenoic acid.

The polyols reacting with the fatty acid include glycols such asethylene glycol, propylene glycol, butylene glycol, hexamethyleneglycol, diethylene glycol and the like, trifunctional polyols such asglycerine, trimethylolpropane, triethanolamine and the like,tetrafunctional polyols such as diglycerine, pentaerythritol and thelike, hexafunctional polyols such as sorbitol and the like,octafunctional polyols such as sugar and the like, and addition polymerssuch as of alkylene oxides corresponding to these polyols and fatty,alicyclic and aromatic amines, and addition polymers such as of thealkylene oxides and polyamide-polyamines. Of these, polyester polyolssuch as glyceride recinoleate, an ester of recinoleic acid and1,1,1-trimethylolpropane are preferred.

(Polyether-Based One)

Polyols of the polyethers include addition polymers such as of dihydricalcohols such as ethylene glycol, diethylene glycol, propylene glycol,dipropylene glycol, 1,3-butanediol, 1,4-butanediol,4,4′-dihyroxyphenylpropne, 4,4′-dihydroxyphenylmethane and the like,trihydric or polyhydric alcohols such as glycerine,1,1,1-trimethylolpropane, 1,2,5-hexanetriol, pentaerythritol and thelike, and alkylene oxides such as ethylene oxide, propylene oxide,butylene oxide, α-olefin oxides and the like.

(Other Types of Polyols)

As other types of polyols, mention is made of polyols having acarbon-carbon main chain, e.g. acrylic polyol, polybutadiene polyol,polyisoprene polyol, hydrogenated polybutadiene polyol, polyols obtainedby graft-polymerizing AN (acrylonitrile) or SM (styrene monomer) to theabove-indicated carbon-carbon polyols, polycarbonate polyols, PTMG(polytetramethylene glycol) and the like.

(Polyisocyanate)

As a polyisocyanate, mention is made of aromatic polyisocyanates,aliphatic polyisocyanates, alicyclic polyisocyanates, and the like.Examples of the aromatic polyisocyanate include diphenylmethanediioscyanate (MDI), polymethylene polyphenylene polyisocyanate (crudeMDI), tolylene diisocyanate (TDI), polytolylene polyisocyanate (crudeTDI), xylene diisocyanate (XDI), naphthalene diisocyanate (NDI) and thelike. Examples of the aliphatic isocyanate include hexamethylenediisocyanate and the like. Examples of the alicyclic polyisocyanateinclude isophorone diisocyanate (IDI) and the like. Besides,polyisocyanates obtained by modifying the polyisocyanates withcarbodiimides (carbodiimide-modified polyisocyanates),isocyanurate-modified polyisocyanates, ethylene oxide-modifiedpolyisocyanates, urethane polymers (e.g. reaction products of polyolsand excess polyisocyanates having an isocyanate group at the molecularterminals) are usable. These may be used singly or in admixture. Ofthese, diphenylmethane diisocyanate, polymethylene polyphenylenepolyisocyanate, carbodiimide-modified polyisocyanates, ethyleneoxide-modified polyisocyanates are preferred.

Depending on the properties of reaction curable resins, characteristicssuch as of heat resistance, flame retardancy, impact resistance,moisture barrier property and the like of the battery pack can beimproved.

For instance, when a urethane resin is used, it is preferred thatdiphenylmethane diisocyanate (MDI), which is an isocyanate having, inaddition to a rigid benzene ring structure, the lowest molecular weight,is used as a hard segment structure and a mixing ratio by weight of apolyol base compound and an isocyanate curing agent (basecompound/curing agent) is set at 1 or below, preferably at 0.7 or below.This eventually leads to a structure that is high crosslinking densityand has a rigid, symmetric molecule chain. Thus, there can be obtained agood heat resistance, good structural strength, improved flameretardancy ascribed to the urethane bonds, and a resin viscosityensuring high fluid chargeability or injectability.

It will be noted that although a higher content of diphenylmethanediisocyanate (MDI) shows better characteristics with respect to strengthand moisture barrier property, its content exceeding 80 wt % leads tothe hard segment structures being too large in number, resulting in thedegradation of impact strength. Where weatherability is required, it ispreferred to mix, with MDI, yellowing-free polyisocyanates based on XDI,IPDI or HDI. In order to enhance a crosslinking density, it is preferredto add low molecular weight trimethylolpropane as a crosslinking agentto the base compound.

When cured, the reaction curable resin should preferably have an impactstrength of not less than 6 kJ/m², more preferably not less than 10kJ/m² when subjected to the Izod V-notch test of JIS K7110. This isbecause when the impact strength is greater than 6 kJ/m², excellentcharacteristics are obtained in a 1.9 m drop test and a 1 m drop test.The impact strength of 10 kJ/m² ensures very excellent characteristicsin the drop tests that are assumed to be highest in the probability ofoccurrence in the marketplace. A higher molecular weight distribution(number average molecular weight/weight average molecular weight) leadsto more improved resin fluidity and moldability, with a tendency thatimpact resistance becomes deteriorated. Accordingly, the fluidity shouldpreferably be, at least, at a level of not less than 80 mPa·second. If aviscosity is controlled within a range of form 200 mPa·second to 600mPa·second, the resin can be favorably used and such a range is morepreferred.

The reaction curable resin should preferably ensure flame retardancywherein a fire spread area is not larger than 25 cm² when determined bya UL746C ¾ inch flame test in a thickness of 0.05 mm to smaller than 0.4mm.

This is because with the flame retardancy of battery pack, no firespread is required in a resin thickness that is as very small as 0.05 mmto smaller than 0.4 mm. This is a very specific and severe requirementwhen taking it into consideration that a resin thickness sufficient tosatisfy UL94VO having very high flame retardancy is at about 3 mm. Itwill be noted that for the purpose of improving flame retardancy, whenan inorganic filler ingredient is added to a reaction curable resin inamounts not smaller than 40 wt %, a pierce resistance is simultaneouslyimproved, but with a tendency that fluidity and impact resistancedegrade. Additionally, non-halogen flame retardancy has to be secured inview of environmental protection. If phosphate ester-based flameretardant materials are added in larger amounts, armor strength becomeslower, resulting in the degradation of weatherability under hightemperature and high humidity conditions.

Where a urethane resin is used as such a reaction curable resin, it ispreferred to include a flame-retardant polyol that has a structurerepresented by the following formula (1). This is because this polyol isable to yield a flame retardant component to the inside of thepolyurethane resin structure, so that especially, when a resin thicknessis small, this polyol is effective in improving the flame retardancyalong with structural strength being ensured.

PO(XR)₃  (1)

wherein R=H, an alkyl group or a phenyl group, X=S, O or N, and n in(CH₂)n, is an integer of 1 or over.

This urethane resin has a unique combustion behavior wherein a burnerflame is applied to a resin piece, under which it instantaneouslywithstand the flame and is subsequently burnt up at once and the fire isextinguished without spread, thus responding for the flame retardancyrequired for a small resin thickness of from 0.05 mm to smaller than 0.4mm. The reason why such a behavior is shown is not known, but thefollowing matter may be considered, for example. That is, the flameretardancy ascribed to the endothermic reaction of ordinaryhalogen-based materials or aluminum hydroxide or the addition ofphosphate esters that are liable to bleed on surfaces should likewisecontribute to carbonization or formation of a heat-insulated layer, butwith a reduced effect. In applications of insert molding of an article,such as a battery, whose resin thickness is small and which has a greatheat capacity, where a combustion energy in the event of the runaway ofa battery is very great, the promotion rate of carbonization, theformation rate of the heat-insulating layer and the location of a flameretardant element are considered to be important for obtaining flameretardancy. As a consequence, a flat sheet making use of a non-halogenresin and reflecting a thickness at the thinnest portion of a batterypack (e.g. from 0.05 mm to 0.4 mm) ensures such flame retardancy at alevel of 25 cm² or below determined by the UL746C ¾ inch flame test.

With the case where such a urethane resin as set out above is not used,a reaction curable resin in a small thickness is able to improve impactstrength if the glass transition point (glass transition temperature) ismade low. Simultaneously, such a small thickness resin is shrunk bymeans of a burner flame and the flame is unlikely to spread owing to theincreased actual thickness of the shrunk resin, thereby improving flameretardancy. On the other hand, if the glass transition point is too lowor two high, strength and safety tend to lower. Accordingly, the glasstransition point of a reaction curable resin is from 60° C. to 150° C.and a melting (decomposition) temperature is preferably from 200° C. to400° C. The glass transition point is more preferably from 85° C. to120° C. The melting (decomposition) temperature is more preferably from240° C. to 300° C. If the glass transition point is lower than 60° C., adifficulty is involved in keeping strength for an armor in an ambienttemperature of 45° C. If the glass transition point exceeds 150° C.,there is concern that the discharge of an energy stored in a battery isdelayed in the course of the misuse, thus leading to a serious accident.

The glass transition temperature is set at 60° C. to 150° C., at whichwhen the melting temperature (decomposition temperature) is set at from200° C. to 400° C., flame retardancy is improved due to the contributionof the endothermic reaction resulting from the melting anddecomposition.

If the melting (decomposition) temperature is lower than 200° C., heatabsorption occurs at the initial stage of the promotion of carbonizationand the formation of the heat-insulating layer, thus not contributing tothe flame retardancy. The melting (decomposition) temperature exceeding400° C. does not contribute to the flame retardancy as well because ofthe delayed timing of heat absorption.

As a result of investigations, it has been found that when structures ofrelatively low molecular weight materials by increasing a content of MDIare increased in number to enhance a crosslinking density, a softeningbehavior at high temperatures becomes faster and higher flexibility isimparted when compared with those of resins of low crosslinkingdensities made of long-chain, rigid polymers. In this way, not onlysimilar reliability can be secured at an ordinary guaranteed temperatureof not higher than 60° C. for use as a battery pack, but also in amalfunction region outside the guaranteed temperature, high reliabilityis obtained wherein the armor is softened within a very short timebefore a high energy density battery is in a major accident such as ofbursting or firing of the battery and the energy is released and a neweffect of showing shape following capability is imparted. In case wherea battery generates a gas and is swollen owing to theoxidation-reduction reaction of an electrolytic solution by misuse in ahigh-temperature region outside the guaranteed temperature, the armorresin of the embodiment of the invention exhibits rubbery physicalproperties at temperatures higher than the glass transition temperature.Thus, the armor is swollen without increasing the inner pressure of thebattery, so that there occurs no further unsafe behavior such as of theinternal short-circuiting of the battery.

It has also been found that with the case of the battery pack of theembodiment of the invention, once a transient high temperature conditionhas been removed, formation gases consisting mainly of carbon dioxideand generated in the battery are absorbed with the negative electrodeand in the electrolytic solution, and a characteristic behavior iscollaterally shown as having never experienced in existing batterypacks, i.e. the swollen molded armor is returned to an original form,like rubber. This is contrary to batteries using an aluminum armor thatis ordinary for square batteries, in which if the aluminum can is onceswollen by an increased inner pressure, the swollen shape suffering agreat dimensional change is held as it is when the inner pressurelowers. This behavior develops without resorting to a specificstructural design and thus, very excellent effects of satisfying avolume energy density and reliability at low costs have been confirmed.

The reaction curable resin should preferably have a viscosity of from 80mPa·second to less than 1000 mPa·second. The coverage failure over themaximum surface of a battery can be avoided by controlling the viscositywithin such a range as indicated above. This in turn suppressescharacteristic degradation of the battery pack. Although the reactioncurable resin is excellent in fluidity because the curing time is longerthan with the case of thermoplastic resins. When the viscosity is high,the mold retention increases, so that a manufacturing apparatus becomesexpensive with poor productivity. Hence, an improvement in volume energydensity and low costs, which are ascribed to the thinning of a moldedmember of the pack that is a characteristic of the battery pack of theembodiment of the invention, cannot be attained. In contrast, when theviscosity is too low, fluidity becomes too high, so that the productionrate lowers owing to burrs from a mold and exudation of a resin towardthe substrate portion, with concern that a percent defective rises.

The reaction curable resin (e.g. a urethane resin) is adhesive in natureand has strong bonding to metals and is able to bond to a thermoplasticresin through polar groups thereof to provide a tough integratedstructure. Although a thermoplastic polyamide resin has bondingproperties, its bonding force is so weak that a physical bondingreinforcement and a high fill pressure are needed. In this connection,however, no such limitation is placed on reaction curable resins.Although the relation between the bonding properties of urethane resinand the aggregation structure is not clear, a tendency has been foundwherein a higher crosslinking density leads to poorer bondingproperties. In view of this, it is preferred to use a bonding memberwherein a number of active hydrogen atoms exist on the surface or amember wherein a number of polar groups that are likely to form ahydrogen bond with a urethane resin exist. Likewise, it is preferredthat an undercut portion is formed at a fit portion with the member toprevent disassociation with the member and that the surface of themember is roughened or slit up thereby increasing a substantial bondingarea. It is also preferred that the aggregation structure of urethaneresin is controlled by controlling the curing temperature conditions tobe at a low temperature so that a number of polar groups of the surfaceis increased, thereby improving bonding properties, or the releaseproperties from a mold is controlled by elevating a temperaturesufficient to lower bonding properties.

(Additives)

The reaction curable resin may be admixed with additives such asfillers, flame retardants, defoamers, bactericides, stabilizing agents,plasticizers, thickening agents, antimold agents, and other types ofresins.

The flame retardants include triethyl phosphate, tris(2,3-dibromopropyl)phosphate and the like. Other additives include fillers such as antimonytrioxide, zeolite and the like, and colorants such as pigments and dyes.

(Catalyst)

Catalysts may be added to the reaction curable resin. The catalyst isadded so as to play a role of causing isocyanate and polyols to bereacted with each other and also isocyanate to be dimerized ortrimerized, for which known catalysts may be used. More specifically,there can be used triethylenediamine, 2-methyltriethylenediamine,tetramethylhexanediamine, pentamethyldiethylenetriamine,pentamethyldipropyltriamine, pentamethylhexanediamine,dimethylaminoethyl ether, trimethylaminopropylethanolamine,tridimethylaminopropylhexahydrotriazine, and tertiary amines such astertiary ammonium salts. A metal-based isocyanuration catalyst ispreferably used within a range of from 0.5 parts by weight to 20 partsby weight per 100 parts by weight of a polyol. If the metal-basedisocyanuration catalyst is smaller than 0.5 parts by weight,isocyanuration does not unfavorably proceed to a satisfactory extent. Ifthe amount of metal-based isocyanuration catalyst is added in amounts ofnot smaller than 20 parts by weight per 100 parts by weight of a polyol,an effect corresponding to the increased amount is not obtained.

As a metal-based isocyanuration catalyst, there are used, for example,fatty acids and metals. More specifically, mention is made of dibutyltinlaurate, lead octylate, potassium ricinoleate, sodium ricinoleate,potassium stearate, sodium stearate, potassium oleate, sodium oleate,potassium acetate, sodium acetate, potassium naphthalate, sodiumnaphthalate, potassium octylate, sodium octylate and mixtures thereof.

Other catalysts include organotin compounds, for which mention is made,for example, of tri-n-butyltin acetate, n-butyltin trichloride,dimethyltin dichloride, dibutyltin dichloride, trimethyltin hydroxideand the like. These catalysts may be used as they are, or may bedissolved in a solvent, such as ethyl acetate, at a concentration of 0.1to 20% and added in an amount of 0.01 to 1 part by weight as a solidcontent per 100 parts by weight of isocyanate. As will be seen from theabove, the catalyst may be formulated as it is or in a condition ofbeing dissolved in a solvent. In either case, it is preferred to add, asa solid content, 0.01 to 1 part by weight, more preferably 0.05 to 0.5parts by weight, per 100 parts by weight of isocyanate. If the amount ofthe catalyst is smaller than 0.01 part, the formation of a polyurethaneresin molded product becomes slow and resinous curing does not occur,thus making the molding difficult. In contrast, when the amount exceeds1 part by weight, the resin formation becomes extremely high and moldingas a shape-retained polymer layer is unlikely to occur.

(Metal Oxide Filler)

A metal oxide filler may be contained in the armor member 40. As a metaloxide filler, mention is made of oxides of silicon (Si), aluminum (Al),titanium (Ti), zirconium (Zr), zinc (Zn) and magnesium (Mg), andmixtures of these oxides. Such a metal oxide filler functions to improvethe hardness of the armor member 40 and is disposed in contact with alayer containing a reaction curable resin. As a matter of course, themetal oxide filler may be incorporated in the layer containing areaction curable resin. In this case, it is preferred that the filler isuniformly dispersed throughout the layer containing a reaction curableresin.

The amount of the metal oxide filler may appropriately vary depending onthe type of polymer of the layer containing a reaction curable resin. Ifthe amount relative to the weight of the reaction curableresin-containing layer is smaller than 3%, the hardness of the armormember may not be satisfactorily increased. On the other hand, if theamount exceeds 60%, there may be presented a problem resulting frommoldability and brittleness of ceramics in the course of manufacture.Thus, it is preferred to incorporate a metal oxide filler in an amountof about 2 to 50% relative to the weight of the reaction curableresin-containing layer.

When an average size of the metal oxide filler is made smaller, hardnessincreases. Nevertheless, filling properties at the time of molding areinfluenced with the possibility that some problem is involved inproductivity. On the other hand, if the average size of the metal oxidefiller is made great, intended strength is unlikely to obtain, thusleading to the possibility that a dimensional accuracy as a battery packcannot be adequately attained. Accordingly, the average size of themetal oxide filler is preferably at 0.1 to 40 μm, more preferably at 0.2to 20 μm.

Further, the metal oxide filler may take various forms such asspherical, flaky, platy, and needle-like forms. Although notspecifically limited, spherical particles are preferred because they areeasy to prepare and are inexpensively available in the form of a uniformaverage size. Needle-shaped particles having a high aspect ratio arepreferred because strength as a filler is likely to increase. Flakyparticles are preferred because filling properties are enhanced when thecontent of the filler increases. It will be noted that althoughdepending on the purpose and type of material, fillers having differentaverage sizes may be mixed, or fillers having different shapes may bemixed.

The armor member 40 may contain, aside from the metal oxide, varioustypes of additives. For instance, in the layer containing a reactioncurable resin, UV absorbers, light stabilizers, curing agents orarbitrary mixtures thereof may co-exist with the metal oxide filler.

(Method of Making a Battery Pack)

Referring to FIGS. 5A to 5D, the method of making a battery pack isillustrated. As shown in FIG. 5A, the frame 30, battery 10, circuitboard 33, PTC element 32 and the like components are integrated by resinmolding to provide a resin molded product, i.e. a battery pack.

Initially, the battery 10 is made in the following way, a positiveelectrode 21 and negative electrode 22, on which a gel electrolyte layerare formed on opposite sides thereof, a separator 23 a are successivelylaminated in the order of the negative electrode 22, separator 23 a,positive electrode 21 and separator 23 a, and the resulting laminate iswound about a flat core and convolutely wound many times to obtain aconvolutely wound battery element. Next, the laminate film 27 issubjected to deep drawing to form a recess 27 a, and the battery element20 is inserted into the recess 27 a. The non-drawn portion of thelaminate film 27 was folded upward to the recess 27 a, after which theouter peripheries along the recess 27 a is heated sealed. In thismanner, the battery 20 is obtained.

Next, the circuit board 33 is accommodated inside and at the front ofthe frame 30 and secured by rivets. A PTC protecting tape 31 and a tubprotecting tape 38 are disposed in position, and the circuit board 33,battery 10, PTC element 32, metal fitting 35 for negative electrode,positive electrode lead 25 a, negative electrode lead 25 b and the likeare connected such as by resistance welding, thus assembling these withthe frame 30. Thus, an assembled body wherein the battery 10, circuitboard 33, frame 30 and other parts have been assembled is obtained.

It will be noted that at a side surface of the frame 30, there areprovided a charge port 70 a for charging a resin into the frame and adischarge portion 70 b for discharging the resin to outside of theframe. This charge port 70 a and discharge port 70 b may be provided atthe front surface and rear surface of the frame 30, respectively.

Next, the assembled body is placed in a molding space of a mold 80 asshown in FIG. 5C. Although not particularly shown, the mold 80 may beprovided with positioning projections (e.g. four projections). Theseprojections serve to place the battery 10 and the like in position.Next, a reaction curable resin, heated to a given temperature, ischarged into the mold from a resin charge port 81, and the resultingresin molding was removed after curing the resin, followed by mold splitand deburr finish to obtain a battery pack shown in FIG. 5D.

It will be noted that when the reaction curable resin is filled in themolding space of the mold 80, it is necessary to generally fill theresin while applying a certain level of compression pressure to thearmor member so as to inhibit a space from being formed in the moldingspace. To cope with this, various measures may be adopted so that thebattery and protecting circuit board are prevented from moving fromgiven positions in the molding space by the pressure-filled reactioncurable resin. For instance, the reaction curable resin may be dividedinto two or more portions and successively charged so that the batteryand the protecting circuit board are, respectively, kept in position inthe molding space by means of a non-charged portion, after which thereaction curable resin is flown in every corner of the molding space ofthe mold. At the same time, for example, there may be used positioningparts in such a way that tapes, rubber pieces and mesh-shaped parts tobe integrally molded are wound about the cell or battery once.Alternatively, after fixing the circuit board 33 to the frame 30, thelaminate film 27 of the battery 10 and the frame 30 may be bondedtogether, thereby permitting the battery 10 and the circuit board 33 tobe kept in position in the molding space.

Although depending on the resin composition of the reaction curableresin, there is concern that heat generation during curing and curingshrinkage in the course of from two-liquid mixing till curing becomevery great. In order to suppress the heat generation during curing, itis preferred that a starting low molecular weight resin having a lowviscosity is charged at a low temperature of not higher than 40° C. andthe mold 80 should be one that has an adequately great capacity and ismade of aluminum or SUS having high thermal conductivity. As to thecuring shrinkage, the mold is preferably so designed as to provide witha resin pool and the resin is charged in amounts much greater than anecessary amount of the resin and the starting resin is supplied, asnecessary, from the resin pool in association with the curing shrinkage.

(Variation)

As the laminate film 27, there may be used, in place of the aluminumlaminate film, those films having single or double or more layers andcontaining a polyolefin film.

The reaction curable resin used in this case is preferably a urethaneresin. Preferably, the urethane resin has a mixing ratio by weight of abase polyol compound and an isocyanate curing agent (basecompound/curing agent) at 1 or below and contains a molecular chainconsisting of diphenylmethane diisocyanate (MDI) in an amount of atleast 20 wt % or more of the total of the base compound and the curingagent. This is because moisture barrier properties of such a urethaneresin are pronouncedly shown. More preferably, the urethane resin has amixing ratio by weight of a base polyol and an isocyanate curing agent(base compound/curing agent) at 0.7 or below and contains a molecularchain consisting of diphenylmethane diisocyanate (MDI) in an amount ofat least 40 wt % or more of the total of the base compound and thecuring agent, for which the moisture barrier properties of the resultingurethane resin are more improved.

Using such a urethane resin, the armor member 40 is imparted withexcellent moisture barrier properties. Accordingly, there may be used,instead of an aluminum laminate film, a single or double or more filmincluding a polyolefin film.

It is preferred that the polyolefin film is formed with a depositedlayer by vacuum deposition or sputtering so as to enhance moisturebarrier properties. The materials used for the deposited layer includeknown ones such as silica, alumina, aluminum, zinc, zinc alloys, nickel,titanium, copper, indium and the like, of which aluminum is preferred.

The aluminum laminate film should have a thickness of about 20 μm inorder to allow drawing along the thickness of the battery and shouldalso have an about 15 μm to 30 μm thick nylon or PET layer to protectthe aluminum layer upon the drawing. This tends to lower a volume energydensity of the battery pack to an extent of about 10%.

On the other hand, when using a thin polyolefin film, which does notallow permeation of an electrolytic solution of the battery element 20and ensures moisture barrier properties and which is deposited withaluminum on the surface thereof after sealing of the battery element 20,moisture barrier properties can be held by means of an aluminum layerwith a thickness 10 μm or below, which is smaller than the half ofexisting counterparts.

Since no drawing is effected, the nylon or PET layer may be omitted. Inthis case, after armoring the battery element 20 with a single or doublelayer packing film, molding with the urethane resin ensures reliabilityequal to or greater than in related-art ones.

With laminate film packages, there has been concern that when sealed endfaces are folded, moisture infiltration increases owing to the breakageof the aluminum layer and the separation between the aluminum and theCPP layer. Such a failure does not occur because of the moisture barrierproperties imparted with the urethane resin and the aluminum depositionafter the sealing of the battery. In addition, the battery capacity issignificantly improved. Thus, very excellent effects can be obtained.The aluminum deposition is preferably a multilayer deposition of two ormore cycles. With the multilayer deposition, reliability can bemaintained even when the aluminum layer is at 1 μm or below inthickness. If the thickness is smaller than 0.03 μm, there is concernthat pinholes are formed in the deposition surface. Preferably, thealuminum should have a thickness of 0.03 μm or over.

2. Second Embodiment

A battery pack according to the second embodiment of the invention isnow described. It will be noted that illustration on similar points asin the first embodiment may be arbitrarily omitted.

(Structure of a Battery Pack)

FIG. 6A is an exploded, perspective view showing a configuration exampleof a battery pack according to the second embodiment of the invention.FIG. 6B is an appearance perspective view showing a configurationexample of the battery pack.

As shown in FIGS. 6A and 6B, this battery pack includes a frame 30, abattery 10 and a circuit board 33 as essential component elements of thebattery pack. The battery pack is provided with other parts including aPTC element 32, a tub-protecting tape 38, a metal fitting 39 fornegative electrode, a submergence detection seal 36, which are connectedto the essential component elements and/or are disposed in position ofthe essential component elements. The battery pack is made by assemblingthe battery 10, circuit board 33 and other parts including the PTCelement 32, and the frame 30 to obtain an assembled body or assembly,followed by subjecting to molding with a reaction curable resin toobtain an integrated resin molding having a substantially rectangularparallelepiped shape. In this battery pack, the assembly of the battery10, circuit board 33 and other parts including the PTC element 32 isarmored with the frame 30 and an armor member 40. The battery is coveredentirely with the armor member 40. Moreover, the battery 10 is coveredwith the frame 30 through the armor member 40 at the side surfaces andpart of the upper and lower surfaces of the battery 10.

(Frame)

The frame 30 has a shape corresponding to that of the battery withrespect to the front and rear surfaces, left side surface, right sidesurface and upper and lower surfaces and has a space capable ofaccommodating the battery 10 therein. When assembling with the battery10, the upper and lower surfaces of the frame 30 are, respectively, soshaped as to be partly cut away inside the surface in a rectangular formthat permits part of the upper and lower surfaces of the battery 10 tobe exposed.

The frame 30 has a space capable of accommodating the circuit board 33at the inner side of the left side surface and the circuit board 33 isplaced in this space. The circuit board 33 is fixed in intimate contactwith the inner surface of the frame 30 by rivets. The frame 30 isprovided with a plurality of openings 34 at the left side surfacethereof and the contacts of the circuit board 33 accommodated in theframe 30 are permitted connection to outside through the openings 34.

(Method of Making the Battery Pack)

This battery pack can be made similarly to the first embodiment.

3. Third Embodiment

A battery pack according to the third embodiment of the invention isillustrated. It will be noted that illustration on similar points as inthe first embodiment may be arbitrarily omitted.

(Structure of a Battery Pack)

FIG. 7A is an exploded, perspective view showing a configuration exampleof a battery pack according to the third embodiment of the invention.FIG. 7B is an appearance perspective view showing a configurationexample of the battery pack. FIG. 8A is a sectional view taken alongline c-c′ of FIG. 7B. FIG. 8B is a sectional view taken along line d-d′of FIG. 7B.

As shown in FIGS. 7A and 7B, this battery pack includes a frame 30, onemetal sheet 51, a battery 10 and a circuit board 33 as essentialcomponent elements of the battery pack. The battery pack is providedwith other parts including a PTC protecting tape 31, a PTC element 32, ametal fitting 35 for negative electrode, a submergence detection seal36, which are connected to the essential component elements and/or aredisposed in position of the essential component elements. The batterypack is made by assembling the battery 10, circuit board 33 and otherparts including the PTC element 32, and the one metal sheet 51 and theframe 30 to obtain an assembly, followed by subjecting to molding with areaction curable resin to obtain an integrated resin molding having asubstantially rectangular parallelepiped shape. In this battery pack,the assembly of the battery 10, circuit board 33 and other partsincluding the PTC element 32 is armored with the frame 30, the one metalsheet 51 and an armor member 40. As shown in FIGS. 8A and 8B, thebattery is covered entirely with the armor member 40. Moreover, thebattery 10 is covered with the frame 30 through the armor member 40 atthe side surfaces and part of the upper and lower surfaces of thebattery 10. The battery is covered, at the upper surface, with the metalsheet 51, which is in turn covered with the armor member 40.

(Metal Sheet)

The metal sheet 51 is rectangular in shape and one sheet is placed onthe upper surface of the battery 10. This metal sheet 51 serves as aspacer for positioning parts including the battery 10 when subjected toresin molding. The metal sheet 51 is made of aluminum, stainless steelsor the like. This metal sheet 51 is able to improve a resistance topiercing load. The metal sheet 51 placed on the upper surface of thebattery 10 enables the thickness at a maximum surface to be small,thereby improving a volume energy density.

(Method for Making the Battery Pack)

The frame 30, battery 10, metal plate 51, circuit board 33 and otherparts including the PTC element are integrated by resin molding toobtain a resin molding, i.e. a battery pack.

Initially, a battery is made. Next, the circuit board 33 is accommodatedat an inner side of the front surface of the frame 30 and fixed withrivets. The PTC protecting tape 31 and the tub-protecting tape 38 areplaced in position, and the circuit board 33, battery 10, PTC element32, a metal fitting for negative electrode 35 and a positive electrodelead 25 a and a negative electrode lead 25 b are connected such as byresistance welding, which are assembled with the metal sheet 51 and theframe 30. In this way, there is obtained an assembly including thebattery 10, circuit board 33, metal sheet 51, the frame 30 and otherparts. Next, this assembly is placed in a molding space of a mold 80. Areaction curable resin, heated to a given temperature, is charged intothe mold from a resin charge port 81 and after curing, the resultingresin molding is taken out, followed by mold split and deburr finish toobtain a battery pack.

4. Fourth Embodiment

(Structure of a Battery Pack)

A battery pack according to the fourth embodiment of the invention isillustrated. It will be noted that illustration on similar points as inthe third embodiment may be arbitrarily omitted. FIG. 9A is an exploded,perspective view showing a configuration example of a battery packaccording to the fourth embodiment of the invention. FIG. 9B is anappearance perspective view showing a configuration example of thebattery pack. FIG. 10A is a sectional view taken along line p-p′ of FIG.9B. FIG. 10B is a sectional view taken along line q-q′ of FIG. 9B.

As shown in FIGS. 8A and 8B, this battery pack includes a frame 30, twometal sheets 51, a battery 10 and a circuit board 33 as essentialcomponent elements of the battery pack. The battery pack is providedwith other parts including a PTC protecting tape 31, a PTC element 32, ametal fitting 35 for negative electrode, a submergence detection seal36, which are connected to the essential component elements and/or aredisposed in position of the essential component elements. The batterypack is made by assembling the battery 10, circuit board 33 and otherparts including the PTC element 32, and the two metal sheets 51 and theframe 30 to obtain an assembly, followed by subjecting to molding with areaction curable resin to obtain an integrated resin molding having asubstantially rectangular parallelepiped shape. In this battery pack,the assembly of the battery 10, circuit board 33 and other partsincluding the PTC element 32 is armored with the frame 30, the two metalsheets 51 and an armor member 40. As shown in FIGS. 10A and 10B, thebattery is covered entirely with the armor member 40. Moreover, thebattery 10 is covered with the frame 30 through the armor member 40 atthe side surfaces and part of the upper and lower surfaces of thebattery 10. The battery is covered, at the upper and lower surfaces,with the metal sheets 51, which are in turn covered with the armormember 40, respectively.

(Method of Making the Battery Pack)

This battery pack can be made in a manner similar to the thirdembodiment.

5. Fifth Embodiment

A battery pack according to the fifth embodiment of the invention isillustrated.

(Structure of a Battery Pack)

FIG. 11A is an exploded, perspective view showing a configurationexample of a battery pack according to the fifth embodiment of theinvention. FIG. 11B is an appearance perspective view showing aconfiguration example of the battery pack. FIG. 12A is a sectional viewtaken along line e-e′ of FIG. 11B. FIG. 12B is a sectional view takenalong line f-f′ of FIG. 11B.

As shown in FIGS. 11A and 11B, this battery pack includes, as essentialcomponent elements, a top cover 60, a U-shaped metal sheet 61, a battery10 and a circuit board 33 along with other parts including an insulationtape 87 and L metal fittings 85 a to 85 b of the battery pack. Thecircuit board 33 is a resin molded board molded along with the top cover60. This battery pack is made by assembling the battery 10, the circuitboard 33 and other parts including the PTC element 32, the top cover 60and the U-shaped metal sheet 61 to obtain an assembly, followed bysubjecting to molding with a reaction curable resin to obtain anintegrated resin molding having a substantially rectangularparallelepiped shape. In this battery pack, the assembly of the battery10, the circuit board 33 and other parts including the PTC element 32 isarmored with the U-shaped metal sheet 61 and an armor member 40.

As shown in FIGS. 12A and 12B, the battery is covered entirely with thearmor member 40. Moreover, the circuit board 33 is disposed at the frontof the battery pack and is covered with the top cover 60. The top cover60 covers the front surface of the battery 10 through the armor member40. Moreover, the battery 10 is covered with the U-shaped metal sheet 61through the armor member 40 at opposite side surfaces and lower surfacethereof.

(U-Shaped Metal Sheet)

The U-Shaped Metal Sheet 61 is a Folded Metal Sheet whose section is inthe form of a U shape formed by folding a rectangular flat metal sheetat opposite ends along short sides of the metal sheet. This U-shapedmetal sheet 61 corresponds to the shape of the battery 10 as created bythe main surface having a maximum area and the right side surface andleft side surface formed by the folding of the flat metal sheet, therebyforming a space sufficient to accommodate the battery 10. It will benoted that the shape of the U-shaped metal sheet is not limited to onementioned above. For instance, there may be used one which is formed byfolding the opposite ends along the short side of a rectangular flatmetal sheet and one end along the length thereof. Thus, the U-shapedmetal sheet 61 corresponds to the shape of the battery 10 through theright side surface, left side surface and rear side surface formed byfolding the flat metal sheet, thereby forming a space sufficient toreceive the battery 10.

The U-shaped metal sheet 61 is made of aluminum, a stainless steel orthe like.

(Top Cover)

The top cover 60 is a resin molding provided at the front side of thebattery pack. The top cover is preferably formed of a thermoplasticresin such as a polycarbonate, polypropylene, a polyamide for the reasonset out with respect to the frame 30. The circuit board 33 is a resinmolded board molded along with the top cover 60. It is to be noted thatthe circuit board 33 may be separately provided, in which the circuitboard is fixed to the inner surface of the top cover 60 by rivets.

The top cover is disposed at the front end portion of the U-shaped metalsheet and the positive electrode lead 25 a and the negative electrodelead 25 b connected to the circuit board 33 is placed in the top cover60. The top cover 60 enables the circuit board 33 to be reliablypositioned in the molding step of a reaction curable resin.

(Method for Making the Battery Pack)

The top cover 60, the U-shaped metal sheet 61, the battery 10, thecircuit board 33 and other component parts including the PTC element 32are integrated by resin molding to provide a resin molded product, i.e.a battery pack.

Initially, the battery is made. The circuit substrate 33 is moldedtogether with the top cover 60. The insulating tape 87 is disposed inposition, and the circuit board 33, the PTC element 32, the L metalfittings 85 a to 85 b, the positive electrode lead 25 a and the negativeelectrode lead are connected by resistance welding, followed byassembling the U-shaped metal sheet 61 and the top cover 60 to obtain anassembly.

Next, this assembly is mounted in a molding space of the mold 80.Thereafter, a reaction curable resin, heated to a given temperature, ischarged into the mold from the resin charge port and cured, and theresulting resin molding is taken out, followed by mold split and deburrfinish to obtain a battery pack.

6. Sixth Embodiment

A battery pack according to the sixth embodiment of the invention isdescribed.

(Structure of a Battery Pack)

FIG. 13A is an exploded, perspective view showing a configurationexample of a battery pack according to the sixth embodiment of theinvention. FIG. 13B is an appearance perspective view showing aconfiguration example of the battery pack. FIG. 14 is a sectional viewtaken along line g-g′ of FIG. 13B.

As shown in FIGS. 13A and 13B, this battery pack includes a frame 30,spacers 90, a battery 10 and a circuit board 33, and other partsincluding an insulation tape 87 and L metal fittings 85 a to 85 b. Thecircuit board 33 is a resin molded board molded along with the frame 30.This battery pack is an integrated resin molding substantially in theform of a rectangular parallelepiped and is obtained by assembling thebattery 10, the circuit board 33, the spacer 90, other parts includingthe PTC element 32 and the frame 30 to obtain an assembly, andsubjecting the assembly to resin molding with a reaction curable resin.In this battery pack, the assembly of the battery 10, the circuit board33 and other parts including the PTC element 32 is armored with theframe 30 and an armor member 40.

As shown in FIG. 14, the spacers 90 are disposed at the left sidesurface and right side surface of the battery 10 and also at part of theupper and lower surfaces. The battery disposed with the spacers 90 iscovered entirely with the armor member 40. The frame 30 covers the leftside surface and right side surface of the battery 10 through the armormember 40. Although not shown in the figures, the frame 30 covers thefront and rear surfaces of the battery 10 through the armor member 40.

(Spacer)

The spacers 90 cover the left side surface and right side surface and apart of the upper surface and a part of the lower surface of the battery10. The spacers 90 function to position the components of the batterypack and also to control the flow channel of a resin at the time ofresin molding. More particularly, the spacer 90 has a flow channelcontrol configuration for increasing a fluid resistance such as ofzigzags repeated along the length of the battery. Referring now to FIGS.15A and 15B, the flow channel control configuration is brieflydescribed. For example, as shown in FIG. 15A, when two sides along thelength of the spacer 90 is linear, flow channel 1 and flow channel 2through which a resin flows, respectively, permit similar degrees offluidity. On the other hand, as shown in FIG. 15B, in case where thespacer has zigzags repeated along one lengthwise side of the spacer andis linear along the other side, a resin becomes unlikely to flow at flowchannel 1 to an extent of about two times less than at flow channel 2.

When such a flow channel control configuration is set at an appropriateposition so as to increase a fluid resistance of a resin flown in duringresin molding, the fluidity of the resin at arbitrary portions of thebattery pack is controlled so as to suppress the resin from not runningthrough portions unlikely to be charged. For example, in order toimprove strength of the battery pack, if a difference is made betweenthickness D2 at a short side portion and thickness D3 at a long sideportion and thickness D1 at the maximum area, resin charge is delayed ata portion where a space is great from the structural standpoint of thebattery pack (e.g. a molding space provided to ensure the thickness D2at the short side portion and the thickness D3 at the long sideportion). This enables the maximum area, where the resin is unlikely tobe charged, to be covered satisfactorily.

The shape for imparting a function of controlling the flow channel ofresin is not limited to a zigzag shape wherein triangular cutouts aremade, but various shapes may be used including an indented shape whereintrapezoidal cutouts are made as shown in FIG. 16A, and a wave shape ofdull-angled cutouts as shown in FIG. 16B. If the cutouts are sharplyangled, foams generated at the time of resin charge are liable to remainat valley portions, adversely influencing the appearance and strength.Thus, a blunt angle of not smaller than 60° is preferred and a shapethat is free of portions allowing foams to be accumulated such as inwave forms is preferred. It is preferred that as to how manyfold theflow channel length is increased depending on the shape of cutouts, theflow channel is so designed to come close to a ratio between the shortside thickness D2 or a long side thickness D3) and the maximum surfacethickness D1.

Mesh-shaped, fibrous or porous materials may be used as a material forthe spacer. This enables both an improvement in flow channel controlfunction by allowing a resin to be flown inside the spacer if anoccupied area of the spacer 90 becomes great and also an improvement instrength as a result of taking the resin in the spacer 90 and integralmolding to be achieved.

Although the spacer 90 used includes any of known materials such asmetal sheets, resin covers, self-adhesive tapes and the like. Of these,a fibre cloth tape is preferred in view of simplicity of fixing. Glasscross tapes and cloth tapes using PET as a substrate are much preferred.Tapes making use of polyethylene tend to be poor in adhesion to amolding resin. Although rubbers, acrylic and silicone self-adhesivelayers may be used, acrylic ones are preferred when taking, aside fromadhesiveness and strength, a side reaction of the adhesive layer with areaction curable resin into account.

(Method of Making the Battery Pack)

The frame 30, the battery 10, the spacer 90, the circuit board 33 andother components including the PTC element 32 are integrated by resinmolding to obtain a resin molding, i.e. a battery pack.

Initially, a battery is made. The circuit board 33 is molded along withthe frame 33. An insulating tape 87, etc., are placed in position andthe circuit board 33, the PTC element, the L metal fittings 85 a to 85 band tubs are electrically connected such as by resistance welding,followed by assembling with the frame 30 to obtain an assembly.

It will be noted that although not particularly shown, the frame 30 isprovided with a charge port for charging a resin and a discharge portfor discharging the resin. The charge and discharge ports are provided,for example, at a rear surface of the frame 30. Alternatively, they maybe provided at a front surface, right side surface or left side surfaceof the frame. The charge and discharge ports are preferably provided atthe front and rear surfaces having a great resin charge capacity. Forinstance, where the charge port is provided at a front surface of theframe 30 and the discharge portion is provided correspondingly to a rearsurface of the frame 30, the spacer 90 is preferably disposed on a sideconnecting the charge and discharge ports. Although the frame 30 has aconfiguration wherein an accommodation portion for the circuit board isprovided at a front side, the accommodation portion of the circuit boardis provided at a side face side to accommodate the circuit boardtherein. In this case, the charge and discharge ports are preferablydisposed at the right side surface and left side surface, respectively.

Next, the assembly is placed in a molding space of the mold 80. Areaction curable resin, heated to a preset temperature, is charged intothe mold from the resin charge port. It will be noted that the resin isflown into the frame through the charge port of the frame. Thereafter,after curing of the resin, the resulting resin molding is taken out,followed mold split and deburr finish to obtain a battery pack.

7. Seventh Embodiment

A battery pack according to the seventh embodiment of the invention isillustrated. Similar points as in the sixth embodiment are arbitrarilyomitted.

(Structure of a Battery Pack)

FIG. 17A is an exploded, perspective view showing a configurationexample of a battery pack according to the seventh embodiment of theinvention. FIG. 17B is an appearance perspective view showing aconfiguration example of the battery pack. FIG. 18 is a sectional viewtaken along line h-h′ of FIG. 17B.

As shown in FIGS. 17A and 17B, this battery pack includes a top cover60, a spacer 90, a battery 10 and a circuit board 33 as essentialcomponent elements of the battery pack and other parts including aninsulating tape 87 and L metal fittings 85 a to 85 b. The circuit board33 is a resin molded board molded along with the top cover 60. Thisbattery pack is made by assembling the battery 10, the circuit board 33,the top cover 60 and the spacer 90, and other parts including the PTCelement 32 to obtain an assembly, followed by subjecting to molding witha reaction curable resin to obtain an integrated resin molding having asubstantially rectangular parallelepiped shape. In this battery pack,the assembly of the battery 10, the circuit board 33 and other partsincluding the PTC element 32 is armored with the top cover 60 and anarmor member 40.

As shown in FIG. 18, the spacers 90 are disposed at the left sidesurface and right side surface of the battery 10 and also at part of theupper and lower surfaces. The battery disposed with the spacers 90 iscovered entirely with the armor member 40. Although not shown in thefigures, the top cover 60 covers the front surface of the battery 10through the armor member 40.

(Method of Making the Battery Pack)

The top cover 60, the battery 10, the spacer 90, the circuit board 55and other components including the PTC element 32 are integrated byresin molding to obtain a resin molded product, i.e. a battery pack.

Initially, the battery is made. The circuit board 33 is molded alongwith the top cover 60. The insulating tap 87 is placed in position, andthe circuit board 33, the PTC element 32, the L metal fittings 85 a to85 b and tubs are electrically connected by resistance welding, followedby assembling with the top cover 60 to obtain an assembly. It will benoted that although not particularly shown, the top cover 60 is providedwith a charge port for charging a resin and a discharge port fordischarging the resin.

Next, the assembly is placed in a molding space of a mold 80. A reactioncurable resin, heated to a preset temperature, is charged from the resincharge port into the mold. It will be noted that the resin is flown inthe top cover through the charge port of the top cover. After curing,the resulting resin molding is taken out, followed by mold split anddeburr finish to obtain a battery pack.

EXAMPLES

The invention is more particularly illustrated by way of examples, whichshould not be construed as limiting the invention thereto. The viscosityand MDI content of reaction curable resin used in the examples andcomparative examples were measured in the following way.

(Measurement of Resin Viscosity)

There was estimated a viscosity at a discharge temperature based on amethod of measuring a viscosity at a constant shear rate by use of arotary viscometer for plastic/liquid, emulsified or dispersed resinsdescribed in JIS K7117-2. The rotary viscometer used was the HAAKERotoVisco RV 1 and the viscosity was estimated from viscosity η=τ shearstress)/γ& shear rate). The frequency was set at 3 Hz and although ameasuring temperature was the same as a discharge temperature, dischargeat a normal temperature was made on this occasion and the measurementwas carried out at 25° C. The viscosity was determined at the time of 30seconds after commencement of mixing two fluids of a base resincomponent and a curing agent under agitation.

(Identification of Isocyanate Species by Pyrolysis Gas Chromatography)

There were used, as a pyrolyzer, PY2020D made by Frontier LaboratoriesLtd. and, as a mass spectrometer, JMS-T 100 GC made by Jeol Ltd. Thepyrolysis temperature was set at 550° C., a carrier gas flow rate of thepyrolyzer set at 30 ml/minute and a split ratio set at 30:1 therebysetting the flow rate of the column at 1 ml/minute. The columntemperature was raised at a rate of 5° C./minute from 50° C. to 300° C.,at which the temperature was kept. A detector used was a hydrogen flameionization detector FID. The amount of a sample was at 0.1 mg.

The attributes of peaks on the resulting pyrogram relied on library, a38 minute peak was attributed as diphenylmethane diisocyanate and a 21minute peak was as 2,4- and 2,6-tolylene diisocyanate. As to a urethaneresin, although there were found peaks of products resulting from thecleavage of the urethane bond by pyrolysis and the cleavage of the esteror ether bond, no mixed fragment of both isocyanate and polyolcomponents was observed. A ratio of a peak area of an isocyanate speciesto that of all peaks was determined, revealing that an existing ratio ofa curing agent in cured resin to an amount of a charged curing agent wasnot varied.

Example 1

A battery pack having a structure shown in FIGS. 1A and 1B was made.Initially, a lithium ion secondary battery wherein a battery element wasarmored with an aluminum laminate film was provided. Separately, apolycarbonate frame was obtained by resin molding. A circuit board usedwas a resin molded board obtained by molding a circuit board along withthe frame. Next, the lithium ion secondary battery, the circuit boardand other parts including a PTC element were placed in position and/orthe respective parts were connected by resistance welding to provide anassembly, followed by further assembling with the frame. In this way,there was obtained an assembly of the frame, the circuit board, thelithium ion secondary battery and other battery pack components. Thisassembly was inserted into and fixed in a molding space of a mold. Thepositioning was made with the aid of projections provided in the mold.

Thereafter, at the time when a reaction curable resin, indicated inTable 1, was charged from a resin charge port of the mold and dischargedfrom a resin discharge port of the mold, the reaction curable resin wascured by allowing to stand in a thermostatic chamber set at atemperature (120° C.) indicated in Table 1 for a time (30 minutes)indicated in Table 1. Next, mold split and deburr finish were carriedout to obtain a battery pack.

Example 2

A battery pack was obtained in the same manner as in Example 1 exceptthat a polypropylene frame was used in placed of the polycarbonateframe, the circuit board was fixed to the inner front surface of theframe by rivets without molding the circuit board along with the frame,the reaction curable resin was one indicated in Table 1, and thereaction curable resin was cured by allowing to stand in thethermostatic chamber set at a temperature (110° C.) indicated in Tablefor a time (20 minutes) indicated in the table.

Example 3

A battery pack was obtained in the same manner as in Example 1 exceptthat the structure shown in FIGS. 6A and 6B was adopted, a polypropyleneframe was used in placed of the polycarbonate frame, and the reactioncurable resin was one indicated in Table 1 and was cured by allowing tostand in the thermostatic chamber set at a temperature (100° C.)indicated in Table for a time (20 minutes) indicated in the table.

Example 4

A battery pack was obtained in the same manner as in Example 3 exceptthat the circuit board was fixed to the inner top surface of the frameby rivets without molding the circuit board along with the frame, andthe reaction curable resin was one indicated in Table 1 and was cured byallowing to stand in the thermostatic chamber set at a temperature (90°C.) indicated in Table for a time (15 minutes) indicated in the table.

Example 5

A battery pack having a structure shown in FIGS. 7A and 7B was made.That is, a lithium ion secondary battery similar to that of Example 1was provided. A circuit board was fixed to an inner front surface of apolypropylene frame by rivets without molding the circuit board alongwith the frame. Next, the lithium ion secondary battery, an aluminumsheet, the circuit board and other parts including a PTC element wereplaced in position and/or connected with each other such as byresistance welding, followed by assembling with the frame. Thus, therewas obtained an assembly including the frame, the aluminum sheet, thecircuit board, the lithium ion secondary battery and other battery packcomponents. Next, the assembly was inserted into and fixed in a moldingspace of a mold. The positioning was made by use of the aluminum sheetserving as a spacer.

Thereafter, at the time when a reaction curable resin, indicated inTable 1, was charged from a resin charge port of the mold and dischargedfrom a resin discharge port, the reaction curable resin was cured byallowing to stand in a thermostatic chamber set at a temperature (85°C.) indicated in Table 1 for a time (10 minutes) indicated in the table.Next, mold split and deburr finish were carried out to obtain a batterypack.

Example 6

A battery pack was made in the same manner as in Example 5 except that areaction curable resin used was one indicated in Table 1, positioning inmolding process was made with the aid of projections formed in a mold,and the reaction curable resin was cured by allowing to stand in athermostatic chamber set at a temperature (80° C.) indicated in Table 1for a time (10 minutes) indicated in the table.

Example 7

A battery pack was made in the same manner as in Example 5 except thatthe reaction curable resin used was one indicated in Table 1 and wascured by allowing to stand in a thermostatic chamber set at atemperature (80° C.) indicated in Table 1 for a time (5 minutes)indicated in the table.

Example 8

A battery pack having a structure shown in FIGS. 9A and 9B was made inthe same manner as in Example 5 except that a polycarbonate frame wasused in place of the polypropylene frame, positioning in molding processwas made with use of two aluminum sheets, and the reaction curable resinused was one indicated in Table 1 and cured in a thermostatic chamberset at a temperature (80° C.) indicated in Table 1 for a time (10minutes) indicated in the table.

Example 9

A battery pack having a structure shown in FIG. 11 was made. Initially,a lithium ion secondary battery as used in Example 1 was provided. Acircuit board was fixed to an inner face of a polyamide top cover byrivets. Next, the lithium ion secondary battery, the circuit board andother parts including a PTC element were placed in position and/orconnected such as by resistance welding for assembling, followed byfurther assembling with the top cover and an aluminum U-shaped sheet. Inthis way, the top cover, the U-shaped metal sheet, the circuit board,the lithium ion secondary element and other battery pack components wereassembled to obtain an assembly. This assembly was inserted into amolding space of a mold and fixed. Positioning was made by means of thealuminum U-shaped sheet.

Thereafter, at the time when a reaction curable resin, indicated intable 1, was charged from a resin charge port of the mold and dischargedfrom a resin discharge port, the reaction curable resin was cured byallowing to stand in a thermostatic chamber set at a temperature (80°C.) indicated in Table 1 for a time (5 minutes) indicated in the table.Next, mold split and deburr finish were made to obtain a battery pack.

Example 10

A battery pack was made in the same manner as in Example 9 except that aSUS U-shaped sheet was used in placed of the aluminum U-shaped sheet,and the reaction curable resin used was one indicated in table 1 andcured by allowing to stand in a thermostatic chamber set at atemperature (80° C.) indicated in Table 1 for a time (5 minutes)indicated in the table.

Example 11

A battery pack having a structure shown in FIG. 13 was made. Initially,a lithium ion battery as used in Example 1 was provided. A circuit boardwas not integrated with a frame by resin molding, but was fixed to theinner face at a top side of a polycarbonate frame by rivets. Next, thelithium ion secondary battery, a polyethylene tape spacer (of a straightform), the circuit board and parts including a PTC element were placedin position and/or connected such as by resistance welding forassembling, followed by further assembling with a frame. Thus, there wasobtained an assembly of the frame, the spacer, the circuit board, thelithium ion secondary battery and other battery pack components. Next,this assembly was inserted into and fixed in a molding space of a mold.Positioning was made by means of the spacer.

Thereafter, at the time when a reaction curable resin, indicated intable 1, was charged from a resin charge port of the mold and dischargedfrom a resin discharge port, the reaction curable resin was cured byallowing to stand in a thermostatic chamber set at a temperature (80°C.) indicated in Table 1 for a time (5 minutes) indicated in the table.Next, mold split and deburr finish were made to obtain a battery pack.

Example 12

A battery pack was made in the same manner as in Example 11 except thata paper tape spacer (straight form) was used in place of thepolyethylene tape spacer, the reaction curable resin used was oneindicated in Table 1, and the reaction curable resin was cured byallowing to stand in a thermostatic chamber set at a temperature (80°C.) indicated in Table 1 for a time (5 minutes) indicated in the table.

Example 13

A battery pack was made in the same manner as in Example 11 except thata normex tape spacer (zigzag form) was used in place of the polyethylenetape spacer, and the reaction curable resin used was one indicated inTable 1 and was cured by allowing to stand in a thermostatic chamber setat a temperature (80° C.) indicated in Table 1 for a time (5 minutes)indicated in the table.

Example 14

A battery pack was made in the same manner as in Example 11 except thata normex tape spacer (zigzag form) was used in place of the polyethylenetape spacer, and the reaction curable resin used was one indicated inTable 1 and was cured by allowing to stand in a thermostatic chamber setat a temperature (80° C.) indicated in Table 1 for a time (4 minutes)indicated in the table.

Example 15

A battery pack was made in the same manner as in Example 11 except thata normex tape spacer (indented form) was used in place of thepolyethylene tape spacer, the reaction curable resin used was oneindicated in Table 1 and was cured by allowing to stand in athermostatic chamber set at a temperature (80° C.) indicated in Table 1for a time (3 minutes) indicated in the table.

Example 16

A battery pack having a structure shown in FIG. 17 was made. Initially,a lithium ion battery as used in Example 1 was provided. A circuit boardwas not integrated with a frame by resin molding, but was fixed to theinner face at a top side of a polycarbonate top cover by rivets. Next,the lithium ion secondary battery, a normex spacer (of an indentedform), the circuit board and parts including a PTC element were placedin position and/or were connected such as by resistance welding and thusassembled, followed by further assembling with the top cover. Thus,there was obtained an assembly of a frame, the top cover, the circuitboard, the lithium ion secondary battery and other battery packcomponents. Next, this assembly was inserted into and fixed in a moldingspace of a mold. Positioning was made by means of the spacer.

Thereafter, at the time when a reaction curable resin, indicated intable 1, was charged from a resin charge port of the mold and dischargedfrom a resin discharge port, the reaction curable resin was cured byallowing to stand in a thermostatic chamber set at a temperature (80°C.) indicated in Table 1 for a time (2 minutes) indicated in the table.Next, mold split and deburr finish were made to obtain a battery pack.

Example 17

A battery pack was made in the same manner as in Example 16 except thata glass cloth tape spacer (wave-shaped form) was used in place of thenormex tape spacer, and the reaction curable resin used was oneindicated in Table 1 and was cured by allowing to stand in athermostatic chamber set at a temperature (75° C.) indicated in Table 1for a time (1 minute) indicated in the table.

Example 18

A battery pack was made in the same manner as in Example 16 except thata polyamide top cover was used in placed of the polycarbonate top cover,the circuit board was molded along with the top cover, a PET tape spacer(wave-shaped form) was used in place of the normex tape spacer, and thereaction curable resin used was one indicated in Table 1 and was curedby allowing to stand in a thermostatic chamber set at a temperature (50°C.) indicated in Table 1 for a time (1 minute) indicated in the table.

Comparative Example 1

A battery pack was made in the same manner as in Example 1 except thatthe reaction curable resin used was one indicated in Table 1 and wascured by allowing to stand in a thermostatic chamber set at atemperature (120° C.) indicated in Table 1 for a time (20 minutes)indicated in the table.

Comparative Example 2

A battery pack was made in the same manner as in Example 1 except that apolyethylene terephthalate (PET) frame was used in place of thepolycarbonate frame, and the reaction curable resin used was oneindicated in Table 1 and was cured by allowing to stand in athermostatic chamber set at a normal temperature as indicated in Table 1for a time (one day) indicated in the table.

Comparative Example 3

A polypropylene frame was used in place of the polycarbonate frame. Athermoplastic resin indicated in Table 1 was used. Initially, a lithiumion secondary battery wherein an battery element was armored with analuminum laminate was provided. A polypropylene frame integrated with acircuit board disposed on an inner face at a top side thereof wasobtained by resin molding. Next, the lithium ion secondary battery, acircuit board and other parts including a PTC element were placed inposition and/or connected such as by resistance welding and thusassembled, followed by further assembling with the frame. In this way,there was obtained an assembly of the frame, the circuit board, thelithium ion secondary battery and other battery pack components. Next,this assembly was integrally molded with a resin by resin melt extrusionmolding under conditions indicated in Table 1. Thus, a battery pack wasmade.

Comparative Example 4

A battery pack was made in the same manner as in Comparative Example 3except that a polyethylene frame was used in placed of the polypropyleneframe and a thermoplastic resin indicated in Table 1 was used.

Comparative Example 5

A battery pack was made in the same manner as in Comparative Example 3except that a thermoplastic resin indicated in Table 1 was used.

Comparative Example 6

A battery pack was made in the same manner as in Comparative Example 3except that a reaction curable resin indicated in Table 1 was used.

(Evaluation)

The thus made battery packs were evaluated in the following way.

(Thickness at a Thinnest Portion in Molding Thickness (Maximum SurfaceThickness D1), Short Side Thickness D2)

The maximum surface thickness shown in FIGS. 19A and 19B was measured. Athickness of an armor member wherein the main surface of the battery 10was taken as a starting point of measurement was measured at threepoints in the vicinity of the center and an average value thereof wasdetermined as maximum surface thickness D1. The maximum thickness D2 ata short side (a length of the armor member in a short-side directionfrom the most projected point of the battery 10 along the short sidetaken as a starting point of measurement to a front surface of thebattery pack taken as an ending point of measurement) was measured.Moreover, a ratio between the thickness D1 at the maximum surface andthe thickness D2 at the short side portion was calculated. It will benoted that the battery pack shown in FIGS. 19A, and 19B correspond tothe structure of Example 1 (shown in FIG. 1). FIG. 19A schematicallyshows a battery pack and FIG. 19B is a sectional view taken along liner-r′.

(Rated Energy Density)

A cycle of 1 C constant current/constant voltage charge effected to anupper limit of 4.2V for 15 hours and 1 C constant current discharge to acutoff voltage of 2.5 V was repeated and a rated energy density wasdetermined from the first cycle discharge capacity.

Rated energy density (Wh/l)=(average discharge voltage (V)×ratedcapacity (Ah)/battery pack volume (l)

It is to be noted that 1 C indicates a current value capable ofdischarging a theoretical capacity of a battery in one hour.

(Number of Coverage Failures)

1000 battery packs of the respective examples were subjected to castmolding and cured under curing temperature and time conditions indicatedin Table 1 and removed from the mold, followed by appearance inspection.A sample having foams and a portion where no resin was covered by theappearance inspection was counted as a coverage failure. Thoseconditions wherein defective samples were not larger than 26 in numberper 1000 samples (a percent defective was not larger than 0.26%) weredetermined as good conditions.

(Number of Impedance Defects)

The impedance of substrate and protecting element-attached batteriesprior to cast molding of the batteries to be used in battery packs ofthe respective examples was measured under conditions of 1 kHz by use ofBattery Hi-Tester 3561, made by Hioki E.E. Corporation. The substrateand protecting element-attached batteries were each subjected to castmolding and cured under curing temperature and time conditions indicatedin Table 1 and removed from the mold, followed by measuring again theimpedance for electric characteristic inspection. Those samples whoseimpedance was raised to not lower than 5% by the electric characteristicinspection were determined as an impedance defective product.

(Drop Test 1)

In order to observe a variation in mechanical strength of battery packsof the respective examples, 10 battery packs were made in every exampleand all the battery packs were naturally dropped from a height of 2 m ona concrete floor. Ten drops for each battery pack were carried out sothat six flat faces of each battery pack hit on the floor. Damage-freepacks were as accepted and cracked packs or packs whose parts came offwere as rejected.

(Drop Test 2)

A dimensional variation (Δt) was measured after free fall of batterypacks of the respective examples from a height of 1 m on a concretefloor 50 times.

(Maximum Bulge in a Storage Test of 105° C. and 5 Hours)

In order to measure an increase in thickness of battery packs of therespective examples in a storage test at 105° C., 10 battery packs ofeach example were made and subjected to 1 C constant current/constantvoltage charge to an upper limit of 4.2 V for 15 hours at a temperatureof 23° C. A thickness t1 of the charged battery pack prior to thestorage test was measured. The battery pack, charged to 4.2 V, wasstored in a thermostatic chamber set at 105° C. and the thickness of thebattery pack was measured 1 hour, 3 hours and 5 hours after the storage,and a maximum thickness was taken as t2. The maximum bulge was estimatedin terms of dimensional variation Δt=t2−t1 and an average value of Δt ofthe 10 battery packs was calculated.

(Variation in Thickness after Cooling after Storage at 105° C. for 5Hours)

Battery packs after storage at 105° C. for 5 hours were naturally cooledat a normal temperature and thickness t3 of the respective battery packswas measured one day after the cooling. A variation in thickness afterthe cooling was estimated as dimensional variation Δt=t3−t1.

(Flame Retardancy Test)

Based on a UL 746C ¾ inch flame test of the UL standards (UnderwritersLaboratories Inc.), 300 mm×300 mm three flat test pieces, which wereuniformly molded to have the same thickness as at the thinnest portionof battery pack were used, and a burner flame controlled to have a ¾inch flame was applied to a central lower end of the flat test piece andkept for 30 seconds. Thereafter, the burner flame was removed from thetest piece. At an interval of one minute, the burner flame was againapplied to the same portion for further 30 seconds, followed by removingthe burner flame. It was confirmed that a flame combustion durationafter completion of the first and second flame applications was withinone minute and a combustion area of the test piece was an area notgreater than a footprint of the battery pack, i.e. not larger than 25cm². It was decided that the thickness of the test piece was sufficientto satisfy the UL 746 C ¾ inch flame test.

(Izod V-Notch Impact Strength (kJ/m²) of JIS K7110)

An impact resistance at a normal temperature was estimated based on theIzod impact test of JIS K71100. The device used was a digital impacttester DG-UB, made by Toyo Seiki Seisaku-Sho Ltd., and an average valueof five test pieces was obtained.

The results of the measurements are shown in Table 1.

TABLE 1 Thick- ness of alumi- num Manner Content layer of of MDI Vis-Melting depos- Cover position- estimated cos- Glass point ited part ingfrom ity tran- (thermal on Re- (ther- Cover (spacer, thermal of sitionpyroly- pack- action mo- part Fixing mold decom- Alkyl group of flameManner charged point sis) Pack- aging curable plastic (metal Struc- ofprojec- Spacer position retardant polyol containing PO (XR)₃ of Curingresin (Tg) Tm aging material resin resin) sheet) ture substrate tion)material GC-MS R = H wherein X = S, O, N or (CH₂)_(n) curing time fluid(° C.) (° C.) material (μm) Exam- Silic- Poly- Nil FIG. 1  IntergralMold Nil  0 Nil 120° C. 30 990 58 190 Alumi- Nil ple one carbon- moldingprojec- min num  1 ate of tion laminate frame substrate part and resinExam- Epoxy Poly- Nil FIG. 1  Riveted Mold Nil  0 Nil 110° C. 20 900 152410 Alumi- Nil ple resin pro- projec- min num  2 pylene tion laminateframe part Exam- Acrylic Poly- Nil FIG. 6  Intergral Mold Nil  0 Nil100° C. 20 80 150 400 Alumi- Nil ple resin pro- molding projec- min num 3 pylene of tion laminate frame substrate part and resin Exam- Poly-Poly- Nil FIG. 6  Riveted Mold Nil 18 Nil  90° C. 15 180 60 200 Alumi-Nil ple ure- pro- projec- min num  4 thane pylene tion laminate framepart Exam- Poly- Poly- One FIG. 7  Riveted Metal Alumi- 83 Nil  85° C.10 610 80 230 Alumi- Nil ple ure- pro- alumi- sheet num min num  5 thanepylene num serving sheet laminate frame sheet also as a part (frontspacer surface) Exam- Poly- Poly- One FIG. 7  Riveted Mold Alumi- 20 Nil 80° C. 10 200 124 310 Alumi- Nil ple ure- pro- alumi- projec- num minnum  6 thane pylene num tion sheet laminate frame sheet part (frontsurface) Exam- Poly- Poly- One FIG. 7  Riveted Metal Alumi- 80(CH₃CH₂)₂PO—CH₂OCH₂CH₂OH  80° C.  5 600 85 240 Alumi- Nil ple ure- pro-alumi- sheet num min num  7 thane pylene num serving sheet laminateframe sheet also as a part (front spacer surface) Exam- Poly- Poly- TwoFIG. 9  Riveted Metal SUS 20 Nil  80° C. 10 200 124 310 Alumi- Nil pleure- carbon- SUS sheet sheet min num  8 thane ate sheets servinglaminate frame (front also as a part and spacer back surfaces) Exam-Poly- Poly- One FIG. 11 Riveted Metal Alumi- 80 (CH₃CH₂)₂PO—CH₂OCH₂CH₂OH 80° C.  5 600 85 240 Alumi- Nil ple ure- amide alumi- sheet num min num 9 thane top num serving sheet laminate cover U- also as a shaped spacersheet (front surface) Exam- Poly- Poly- One FIG. 11 Riveted Metal SUS 37(CH₃CH₂)₂PO—CH₂P(CH₂CH₂OH)₃  80° C.  5 400 120 300 Alumi- Nil ple ure-amide SUS sheet sheet min num 10 thane top U- serving laminate covershaped also as a sheet spacer back surface) Exam- Poly- Poly- Nil FIG.13 Riveted Straight Poly- 72 (CH₃CH₂)₂PO—CH₂S(CH₂CH₂OH)₃  80° C.  5 400110 260 Alumi- 0.03 ple ure- carbon- spacer ethylene min num 11 thaneate tape laminate frame part Exam- Poly- Poly- Nil FIG. 13 RivetedStraight Paper 40 (CH₃CH₂)₂PO—CH₂N(CH₂OH)₂  80° C.  5 400 110 260 Alumi-10 ple ure- carbon- spacer tape min num 12 thane ate laminate frame partExam- Poly- Poly- Nil FIG. 13 Riveted Zigzag Normex 55(CH₃CH₂)₂PO—CH₂N(CH₂CH₂OH)₂  80° C.  5 400 110 260 Alumi- 2 ple ure-carbon- spacer tape min num 13 thane ate laminate frame part Exam- Poly-Poly- Nil FIG. 13 Riveted Zigzag Normex 60 OP(OPhCH₃)₃  80° C.  4 400110 260 Alumi- 1 ple ure- carbon- spacer tape min num 14 thane atelaminate frame part Exam- Poly- Poly- Nil FIG. 13 Riveted IndentedNormex 70 (PhO)OP(OPhCH₃)₂  80° C.  3 400 110 260 Poly- 0.8 ple ure-carbon- spacer tape min ethylene 15 thane ate film + frame two partlayers of PET film Exam- Poly- Poly- Nil FIG. 17 Riveted Indented Normex60 (PhO)₂OP(OPhCH₃)  80° C.  2 400 110 260 Vacuum- 0.8 ple ure- carbon-spacer tape min deposit- 16 thane ate ed top poly- cover ethylene film +two layers of PET film Exam- Poly- Poly- Nil FIG. 17 Riveted Wave- Glass60 OP(OPh)₃  75° C.  1 400 110 260 Single 0.8 ple ure- carbon- shapedcross min layered 17 thane ate spacer tape vaccum- top deposit- cover edpoly- pro- pylene film Exam- Poly- Poly- Nil FIG. 17 Integral Wave- PET60 (CH₃CH₂)₂PO—CH₂N(CH₂CH₂OH)₂ +   50° C.  1 400 110 260 Single 0.8 pleure- amide molding shaped tape OP(OPhCH₃)₃ min layered 18 thane top ofspacer vaccum- cover substrate deposit- and resin ed poly- pro- pylenefilm Com- Silic- Poly- Nil FIG. 1  Intergral Mold Nil  0 Nil 120° C. 201000 −20 260 Alumi- Nil par- one carbon- molding projec- min num ativeate of tion laminate exam- frame substrate ple part and resin  1 Com-Epoxy Poly- Nil FIG. 1  Intergral Mold Nil  0 Nil Allowed One 70 155 220Alumi- Nil par- resin ethylene molding projec- to stand day num ativetere- of tion at a laminate exam- phthal- substrate normal ple ate andresin temper-  2 frame ature part Com- Ther- Poly- Nil FIG. 1  IntergralMold Nil  0 Nil Resin 20 2000 120 240 Alumi- Nil par- mo- pro- moldingprojec- melt sec num ative plastic pylene of tion extru- laminate exam-ABS frame substrate sion ple part and resin molding  3 at 120° C. Com-Poly- Nil FIG. 1  Intergral Mold Nil  0 Nil Resin 20 1500 110 220 Alumi-Nil par- Ther- ethylene molding projec- melt sec num ative mo- frame oftion extru- laminate exam- plastic part substrate sion ple poly- andresin molding  4 ure- at thane 120° C. Com- Ther- Poly- Nil FIG. 1 Intergral Mold Nil  0 Nil Resin 30 1000 50 190 Alumi- Nil par- mo- pro-molding projec- melt sec num ative plastic pylene of tion extru-laminate exam- poly- frame substrate sion ple amide part and resinmolding  5 at 180° C. Com- Ure- Poly- Nil FIG. 1  Intergral Mold Nil  0Nil 120° C. 30 990 58 190 Alumi- Nil par- thane methyl- molding projec-min num ative meth- of tion laminate exam- acrylate substrate ple frameand resin  6 part Thinnest Ratio Number of Dimensional Maximum portionbetween coverage variation in bulge in a Variation in in molding Maximummaximum failures upon thickness storage thickness Burned Izod thicknessthickness surface charge of after test at afer cooling area V-notched(maximum at a thickness/ reaction 10 cycles 50 cycles 105° C. afterstorage in a UL746C impact surface short side short side Rated E curableresin of of 1 m for at 105° C. ¾ inch strength in thickness portionthickness density (per 1000 2 m drop drop test 5 hours for 5 hours flameJIS K7110 D1/mm) D2/mm (D2/D1) Wh/l samples) test (mm) (mm) (mm)test/cm² (kJ/m²) Example 1  0.38 0.4 1.1 520 19 Ten samples 1.5 1.4 1.325 5 all accepted Example 2  0.35 0.4 1.1 525 16 Ten samples 1.3 1.3 1.225 5 all accepted Example 3  0.35 2.2 6.3 525 26 Ten samples 1.2 1.2 125 5 all accepted Example 4  0.35 0.36 1.0 525 11 Ten samples 0.9 1 0.821 5 all accepted Example 5  0.35 1.8 5.1 525 14 Ten samples 0.7 0.9 0.720 5 all accepted Example 6  0.35 0.45 1.3 525 11 Ten samples 0.6 0.70.3 16 8 all accepted Example 7  0.35 1.1 3.1 525 14 Ten samples 0.4 0.50.1 13 6 all accepted Example 8  0.05 0.09 1.8 555 11 Ten samples 1.1 10.7 24 8 all accepted Example 9  0.05 0.21 4.2 555 13 Ten samples 0.90.8 0.6 20 6 all accepted Example 10 0.3 0.6 2.0 545 9 Ten samples 0.40.5 0.1 13 9 all accepted Example 11 0.3 1.2 4.0 545 9 Ten samples 0.40.5 0.1 12 8 all accepted Example 12 0.15 0.4 2.7 545 8 Ten samples 0.30.3 0 9 10 all accepted Example 13 0.15 0.45 3.0 545 3 Ten samples 0.30.3 0 9 10 all accepted Example 14 0.1 0.2 2.0 550 3 Ten samples 0.3 0.30 9 11 all accepted Example 15 0.1 0.4 4.0 550 2 Ten samples 0.3 0.3 0 812 all accepted Example 16 0.1 0.3 3.0 550 2 Ten samples 0.3 0.3 0 8 12all accepted Example 17 0.1 0.3 3.0 550 0 Ten samples 0.3 0.3 0 8 12 allaccepted Example 18 0.1 0.3 3.0 550 0 Ten samples 0.3 0.3 0 7 12 allaccepted Comparative 0.45 0.5 1.1 500 211  9 samples Broken 1.5 1.3Burnt out 8 example 1  not accepted down before (separated) 50 cyclesComparative 0.38 1.5 3.9 520 157 10 samples Broken 1.5 1.2 Burnt out 4example 2  not accepted down before (cracked) 50 cycles Comparative 0.452.5 5.6 500 Impedance  6 samples Broken 1.5 1.2 Burnt out 10 example 3 failure in not accepted down before all samples (separated) 50 cyclesComparative 0.45 3.5 7.8 500 Impedance  3 samples Broken 1.5 1.2 Burntout 4 example 4  failure in not accepted down before all samples(cracked) 50 cycles Comparative 0.5 4.5 9.0 480 Impedance  8 samplesBroken 1.5 1.3 Burnt out 5 example 5  failure in not accepted downbefore all samples (separated) 50 cycles Comparative 0.04 0.04 1.0 560157 10 samples Broken 1.5 1.3 Burnt out 5 example 6  not accepted downbefore (cracked) 50 cycles

As shown in Table 1, the resin viscosities in Examples 1 to 18 arecontrolled within an optimum range and thus, formation of a number ofcoverage failure products can be suppressed. On the other hand, withComparative Examples 1 to 6, the resin viscosities are outside theoptimum range, a number of coverage failure products were formed.

8. Other Embodiment

The invention is not limited to these embodiments set forth hereinbeforeand many variations and applications may be possible within the scopenot departing from the spirit of the invention. For example, thevariation described in the first embodiment may be applicable to any ofthe second to seventh embodiments. The configurations set out in therespective embodiments may be appropriately combined.

In addition, for example, batteries of the types other than a lithiumion secondary battery may be used and configurations using a pluralityof batteries may be possible. In recent years, there has been used abattery pack wherein a plurality of batteries are integrated such as abattery pack for vehicles which has been put into practice in the formof a nickel hydrogen battery, and a battery pack used in note personalcomputers and power tools. However, with a battery pack provided with aplurality of batteries, the batteries undergo repeated cycles ofexpansion and shrinkage in association with charge and discharge. Eventhough a deformation amount of individual batteries is small, the totalamount cannot be neglected. To cope with this, in the past, it has beento use a cylindrical battery whose deformation amount is small. In thisconnection, however, there arises a problem in that a space betweenadjacent batteries becomes great, so that a volumetric efficiencylowers. This problem has had to be solved. In case where a plurality ofsquare batteries packed with a laminate film are used, it is necessaryto provide a space for absorbing such a dimensional change ordeformation as set out above, heat is generated in association withcharge and discharge cycles and battery units have to be placed atspatial intervals for the purpose of securing insulation associated withhigh voltage. Thus, even when using square batteries whose volumetricefficiency is better than cylindrical batteries, there is a problem inthat a volume energy density cannot be increased. In the practice of theinvention, when using a plurality of batteries, particularly, in theform of square form, there can be provided a battery that is excellentin dimensional accuracy, mechanical strength and heat dissipatingproperties.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The application is claimed as follows:
 1. A battery pack, comprising: abattery having a main surface and side surfaces; a circuit boardconnected to the battery; an armoring member for armoring the battery insuch a way as to expose at least a part of the main surface of thebattery; a resin layer by which the battery, the circuit board, and thearmoring member are integrated into one, the main surface and the sidesurfaces of the battery being covered by said resin layer, wherein thebattery includes a battery element packed with a packaging material,wherein both of the side surfaces of the battery are covered by thearmoring member, with the resin layer interposed therebetween, whereinthe resin layer is formed by curing reaction curable resin that has aviscosity falling within a range from 80 mPa·second inclusive to 1,000mPa·second exclusive, and wherein a thickness of the resin layer on themain surface of the battery is within a range from 0.05 mm inclusive to0.4 mm exclusive.
 2. The battery pack according to claim 1, furthercomprising: a control member, which is provided at a boundary between aside surface of the battery covered with the resin layer and the mainsurface of the battery, and has a control form.
 3. The battery packaccording to claim 2, wherein the control form is a zigzag form, a waveform, or an indented form.
 4. The battery pack according to claim 2,wherein the armoring member has a charge port, through which thereaction curable resin is charged, and a discharge port facing thecharge port, the reaction curable resin being discharged through saiddischarge port, and wherein the control member is located between thecharge port and the discharge port.
 5. The battery pack according toclaim 2, wherein an armored portion covering a side surface of thebattery and including the resin layer is 1.2 times to 6 times as thickas the resin layer covering the main surface of the battery.
 6. Thebattery pack according to claim 1, wherein the armoring member is madeof a resin molding member that contains at least one type ofthermoplastic resin selected from a group consisting of polycarbonate,polypropylene and polyamide.
 7. The battery pack according to claim 1,wherein the armoring member is a metal member made of aluminum orstainless steel.
 8. The battery pack according to claim 1, wherein themetal member is made of a metal sheet that has a U shape in crosssection and includes a main surface sheet portion and two side surfacesheet portions projecting from the main surface sheet portion atrespective two ends thereof; wherein the battery is accommodated in aspace formed by the main surface sheet portion and the two side surfacesheet portions; and wherein both of the side surfaces of the battery andthe main surface of the battery are covered by the armoring member, withthe resin layer interposed therebetween.
 9. The battery pack accordingto claim 1, wherein the circuit board is accommodated in the armoringmember serving as a housing.
 10. The battery pack according to claim 9,wherein the circuit board is fixed to the armoring member by riveting.11. The battery pack according to claim 1, wherein the reaction curableresin is at least one type of resin selected from a group consisting ofurethane resin, epoxy resin, silicone resin and acrylic resin.
 12. Thebattery pack according to claim 11, wherein the reaction curable resinhas a glass transition point falling within a range from 60° C.inclusive to 150° C. inclusive, has a melting point falling within arange from 200° C. inclusive to 400° C. inclusive, and an impactstrength of not less than 6 kJ/m².
 13. The battery pack according toclaim 11, wherein the reaction curable resin is urethane resin, andwherein the urethane resin contains polyol serving as a base componentand isocyanate serving as a curing agent at a mixing ratio (basecomponent/curing agent) by weight of not greater than
 1. 14. The batterypack according to claim 13, wherein the isocyanate curing agent contains20 wt % or greater of a molecular chain made of diphenylmethanediisocyanate (MDI) relative to total amount of the base component andthe curing agent.
 15. The battery pack according to claim 1, wherein thepackaging material is made of a laminate film.
 16. The battery packaccording to claim 15, wherein the laminate film is an aluminum laminatefilm.
 17. The battery pack according to claim 15, wherein the laminatefilm is a single-layer or double-layer film including a polyolefin film.18. The battery pack according to claim 1, wherein an aluminum-depositedlayer is formed on a surface of the packaging material.
 19. A batterypack manufacturing method, comprising: a step of assembling a battery, acircuit board, and an armoring member, said battery having a mainsurface and side surfaces, said circuit board connected to the battery,said armoring member armoring the battery in such a way as to expose atleast a part of the main surface of the battery; a step of placing anassembly made up of the battery, the circuit board, and the armoringmember in a molding space inside a mold; a step of injecting a reactioncurable resin that has a viscosity falling within a range from 80mPa·second inclusive to 1,000 mPa·second exclusive into the mold; and astep of forming a resin layer by which the battery, the circuit board,and the armoring member are integrated into one, the main surface andthe side surfaces of the battery being covered by said resin layer;wherein the battery includes a battery element packed with a packagingmaterial, wherein both of the side surfaces of the battery are coveredby the armoring member, with the resin layer interposed therebetween,and wherein a thickness of the resin layer on the main surface of thebattery is within a range from 0.05 mm inclusive to 0.4 mm exclusive.20. A battery pack, comprising: a battery having a main surface and sidesurfaces, said battery packed with a packaging material; a circuit boardconnected to the battery; a resin layer by which the main surface andthe side surfaces of the battery are covered; and a control member thathas a control form for controlling a fluid resistance of a flow ofreaction curable resin, which cures to form into the resin layer. 21.The battery pack according to claim 20, wherein the control form isformed at a boundary between a side surface of the battery and the mainsurface of the battery.
 22. The battery pack according to claim 20,further comprising: an armoring member for armoring the battery in sucha way as to expose at least a part of the main surface of the battery,wherein the armoring member, the battery, and the circuit board areintegrated into one by the resin layer; and wherein both of the sidesurfaces of the battery are covered by the armoring member, with theresin layer interposed therebetween.
 23. The battery pack according toclaim 20, wherein the channel control form is a zigzag form, a waveform, or an indented form.
 24. The battery pack according to claim 22,wherein the armoring member has a charge port, through which thereaction curable resin is charged, and a discharge port facing thecharge port, the reaction curable resin being discharged through saiddischarge port, and wherein the control member is located between thecharge port and the discharge port.
 25. The battery pack according toclaim 22, wherein an armored portion covering a side surface of thebattery and including the resin layer is 1.2 times to 6 times as thickas the resin layer covering the main surface of the battery.
 26. Thebattery pack according to claim 22, wherein the armoring member is madeof a resin molding member that contains at least one type ofthermoplastic resin selected from a group consisting of polycarbonate,polypropylene and polyamide.
 27. The battery pack according to claim 22,wherein the armoring member is a metal member made of aluminum orstainless steel.
 28. The battery pack according to claim 20, wherein thecircuit board is accommodated in the armoring member serving as ahousing.
 29. The battery pack according to claim 28, wherein the circuitboard is fixed to the armoring member by riveting.
 30. The battery packaccording to claim 20, wherein the reaction curable resin is at leastone type of resin selected from a group consisting of urethane resin,epoxy resin, silicone resin and acrylic resin.
 31. The battery packaccording to claim 30, wherein the reaction curable resin has a glasstransition point falling within a range from 60° C. inclusive to 150° C.inclusive, has a melting point falling within a range from 200° C.inclusive to 400° C. inclusive, and an impact strength of not less than6 kJ/m2.
 32. The battery pack according to claim 30, wherein thereaction curable resin is urethane resin, and wherein the urethane resincontains polyol serving as a base component and isocyanate serving as acuring agent at a mixing ratio (base component/curing agent) by weightof not greater than
 1. 33. The battery pack according to claim 32,wherein the isocyanate curing agent contains 20 wt % or greater of amolecular chain made of diphenylmethane diisocyanate (MDI) relative tototal amount of the base component and the curing agent.
 34. The batterypack according to claim 20, wherein the packaging material is made of alaminate film.
 35. The battery pack according to claim 34, wherein thelaminate film is an aluminum laminate film.
 36. The battery packaccording to claim 34, wherein the laminate film is a single-layer ordouble-layer film including a polyolefin film.
 37. The battery packaccording to claim 20, wherein an aluminum-deposited layer is formed ona surface of the packaging material.
 38. A battery pack manufacturingmethod, comprising: a step of assembling a battery, a circuit board, anda control member, said battery having a main surface and side surfaces,said circuit board connected to the battery, said control member havinga control form for controlling a fluid resistance of a flow of reactioncurable resin, which cures to form into the resin layer; a step ofplacing an assembly made up of the battery, the circuit board, and thecontrol member in a molding space inside a mold; a step of injecting areaction curable resin into the mold; and a step of forming a resinlayer by causing the reaction curable resin to cure, the main surfaceand the side surfaces of the battery being covered by said resin layer;wherein, in the step of injecting the reaction curable resin, the fluidresistance of the flow of the reaction curable resin is controlled bythe control form.